Dash-devices

Added
- [237](https://github.com/plotly/dash/pull/237) Support `aria-*` and `data-*` attributes in all dash html components. These new keywords can be added using a dictionary expansion, e.g. `html.Div(id="my-div", **{"data-toggle": "toggled", "aria-toggled": "true"})`
- [renderer45](https://github.com/plotly/dash-renderer/pull/45) Allow user to choose between React versions '15.4.2' and '16.2.0':
python
import dash_renderer

Set the react version before setting up the Dash application
dash_renderer._set_react_version('16.2.0')

app = dash.Dash(...)


Fixed
- [renderer50](https://github.com/plotly/dash-renderer/pull/50) Update MANIFEST.in to include `react` and `react-dom` bundles for development mode

Added
- [207](https://github.com/plotly/dash/pull/207) Support React components using [Flow](https://flow.org/en/docs/react/) types. `component_loader` now has the following behavior to create docstrings as determined in discussion in [187](https://github.com/plotly/dash/issues/187):
1. If a Dash component has `PropTypes`-generated typing, the docstring uses the `PropTypes`, _regardless of whether the component also has Flow types (current behavior)._
2. Otherwise if a Dash component has Flow types but _not `PropTypes`_, the docstring now uses the objects generated by `react-docgen` from the Flow types.

Fixed
- [renderer42](https://github.com/plotly/dash-renderer/pull/42) Fix [renderer41](https://github.com/plotly/dash-renderer/issues/41) and [renderer44](https://github.com/plotly/dash-renderer/issues/44).
- In some cases, during initialization, callbacks may fired multiple times instead of just once. This only happens in certain scenarios where outputs have overlapping inputs and those inputs are leaves (they don't have any inputs of their own).
- If an output component is returned from a callback and its inputs were _not_ returned from the same input (i.e. they were already visible), then the callback to update the output would not fire. This has now been fixed. A common scenario where this app structure exists is within a Tabbed app, where there are global controls that update each tab's contents and the tab's callback just displays new output containers.

Added
- [190](https://github.com/plotly/dash/pull/190) `exceptions.PreventUpdate` can be raised inside a callback to prevent the callback from updating the app. See https://community.plotly.com/t/improving-handling-of-aborted-callbacks/7536/2.

Removed
- Removes logging from redux middleware from production build based on process.env.NODE_ENV.

Changed
- Many pylint style fixes: [163](https://github.com/plotly/dash/pull/163), [164](https://github.com/plotly/dash/pull/164), [165](https://github.com/plotly/dash/pull/165), [166](https://github.com/plotly/dash/pull/166), [167](https://github.com/plotly/dash/pull/167), [168](https://github.com/plotly/dash/pull/168), [169](https://github.com/plotly/dash/pull/169), [172](https://github.com/plotly/dash/pull/172), [173](https://github.com/plotly/dash/pull/173), [181](https://github.com/plotly/dash/pull/181), [185](https://github.com/plotly/dash/pull/185), [186](https://github.com/plotly/dash/pull/186), [193](https://github.com/plotly/dash/pull/193)
- [184](https://github.com/plotly/dash/pull/184) New integration test framework.
- [174](https://github.com/plotly/dash/pull/174) Submodules are now imported into the `dash` namespace for better IDE completion.

Changed
- 🔒 Remove CSRF protection measures. CSRF-style attacks are not relevant to Dash apps. Dash's API uses `POST` requests with content type `application/json` which are not susceptible to unwanted requests from 3rd party sites. See [141](https://github.com/plotly/dash/issues/141).
- 🔒 `app.server.secret_key` is no longer required since CSRF protection was removed. Setting `app.server.secret_key` was difficult to document and a very common source of confusion, so it's great that users won't get bitten by this anymore :tada:
- 🐞 [renderer22](https://github.com/plotly/dash-renderer/pull/22), [renderer28](https://github.com/plotly/dash-renderer/pull/28) Previously, old requests could override new requests if their response was longer than the new one. This caused subtle bugs when apps are deployed on multiple processes or threads with component callbacks that update at varying rates like urls. Originally reported in [133](https://github.com/plotly/dash/issues/133). This fix should also improve performance when many updates happen at once as outdated requests will get dropped instead of updating the UI. Performance issue with the first PR reported in [renderer27](https://github.com/plotly/dash-renderer/issues/27) and fixed in the second PR.
- [renderer21](https://github.com/plotly/dash-renderer/pull/21) Fix an issue where a callback would be fired excessively. Previously, the callback would be called as many times as it had inputs. Now, it is called less.

Added
- `app.config` is now a `dict` instead of a class. You can set config variables with `app.config['suppress_callback_exceptions'] = True` now. The previous class-based syntax (e.g. `app.config.suppress_callback_exceptions`) has been maintained for backwards compatibility.
- 🐌 Experimental behaviour for a customizable "loading state". When a callback is in motion, Dash now appends a `<div class="_dash-loading-callback"/>` to the DOM. Users can style this element using custom CSS to display loading screen overlays. This feature is in alpha, we may remove it at any time.

Fixed
- Fix a bug from 0.18.2 that removed the ability for dash to serve the app on any route besides `/`.
- Fix a bug from 0.18.0 with the new config variables when used in a multi-app setting, causing config to be shared across apps. Originally reported in https://community.plotly.com/t/flask-endpoint-error/5691/7
- Rename config setting `supress_callback_exceptions` to `suppress_callback_exceptions`. The original spelling is kept for backward compatibility.
- 🐞 (renderer) Fix a bug where Dash would fire updates for each parent of a grandchild node that shared the same grandparent. Originally reported in https://community.plotly.com/t/specifying-dependency-tree-traversal/5080/5
- 🐞 (renderer) Fix a bug where the document title that displays "Updating..." wouldn't change if the callback raised an Exception. Now it will be removed on any response, even a failure.

Added
- [70](https://github.com/plotly/dash/pull/70) 🔧 Add an `endpoint` to each of the URLs to allow for multiple routes.