Inquirer

- Some display fixes on Windows (mainly) and Unix system.
- Internal refactoring of the rendering logic.

Fix list overflow bug when the list contains separators.

- Choices object now take an optional `short` property that'll be use in the prompt summary after a user selected choice.
- Fix bug if using a terminal without defined width (we're now defaulting to 80 chars in that case)

- Fix the bottom bar functionality
- Minor code cleanup

New feature
- `inquirer.createPromptModule(opt)` not take an `option` arguments. These [options will be passed to the readline factory](https://nodejs.org/api/readline.html#readline_readline_createinterface_options).

Bug fix
- Fix 276 and 209: adding a new observer to the process won't duplicate the prompts (basically the prompt processing queue is now a [hot observable](https://github.com/Reactive-Extensions/RxJS/blob/master/doc/gettingstarted/creating.md#cold-vs-hot-observables)).

1. Fix a lot of issues with natural line returns messing inquirer.js prompt re-rendering.
2. The `validate` function now takes the list of current answers as arguments. 198