Plotly

- Previously, using plotly offline required a paid license.
No more: `plotly.js` is now shipped inside this package to allow
unlimited free use of plotly inside the ipython notebook environment.
The `plotly.js` library that is included in this package is free,
open source, and maintained independently on GitHub at
[https://github.com/plotly/plotly.js](https://github.com/plotly/plotly.js).
- The `plotly.js` bundle that is required for offline use is no longer downloaded
and installed independently from this package: `plotly.offline.download_plotlyjs`
is **deprecated**.
- New versions of `plotly.js` will be tested and incorporated
into this package as new versioned pip releases;
`plotly.js` is not automatically kept in sync with this package.

- *Big data* warning mentions `plotly.graph_objs.Scattergl` as possible solution.

- If you're behind a proxy, you can make requests by setting the environmental variable HTTP_PROXY and HTTPS_PROXY (http://docs.python-requests.org/en/v1.0.4/user/advanced/#proxies). This didn't work for streaming, but now it does.

- Sometimes creating a graph with a private share-key doesn't work -
the graph is private, but not accessible with the share key.
Now we check to see if it didn't work, and re-try a few times until
it does.

Added
- The FigureFactory can now create dendrogram plots with `.create_dendrogram`.

Fixed
- Saving "world_readable" to your config file via `plotly.tools.set_config` actually works.

Added
- You can also save `auto_open` and `sharing` to the config file so that you can forget these
keyword argument in `py.iplot` and `py.plot`.