Inquirer

New look

Thanks to sindresorhus, we have a set of new glyph and a refreshed style.

New feature
- `inquirer.registerPrompt()` allow to register custom prompts (plugins!) or overwriting defaults prompts (mocking!)
- `inquirer.restoreDefaultPrompts()` to restore the defaults prompts

Bugs
- `checkbox` prompt failed when used with an asynchronous `validate` method.

Mainly an internal API update. We now use [RxJS](http://reactive-extensions.github.io/RxJS/) internally and provide a few public API surfacing this internal switch.

Reactive JS

[See full doc for details](https://github.com/SBoudrias/Inquirer.js#reactive-interface)
- You can now pass an `Observable` in lieu of a question array. This allow you to programmatically (and progressively) fill up Inquirer question queue.
- Using `inquirer.prompts(prompts).process.subscribe()` you can be notified each time a question is answered.

Features (not Rx specific)
- `filter` functions can now be async.

Bug Fix
- `filter` function on an `input` prompt is not re-runned on the previously filtered value.

- Update the color handling to use [chalk](https://github.com/sindresorhus/chalk). This will allow Inquirer to respect the `--color` and `--no-color` command line flags.

Features
- Input prompt now show filtered value once submitted (97)
- Checkbox prompt can now display disabled choices (92)

Bug fixes
- Allow falsy default values (101)
- Make sure when force closing Inquirer the cursor is restored (107)

- Allow `choice` values to be negative. (98)
- (Internal) Extract Readline fixes into a standalone module

- `list` prompt now accept a String representing the value of the selected choice.
- `checkbox` prompt now accept an Array as default value reprensenting the checked choices values.
- Internal refactoring to build everything out of UI/Layout Object
- New `BottomBar` UI allowing to log content into a stream while keeping a bottom bar updated with status information.
- Refactor how `Separator` are handled because of Node.js "no smart" module caching. Now Separators are objects with `type=separator` property. (The `inquirer.Separator` constructor is still the recommend use, just prefer not checking `instanceof` for detection)