sublime text: build scripts

This PR simplifies build scripts on Windows machines.

### Requirements

- `7z.exe` on the `PATH`\*
- Setting `$STDataPath` to point to Sublime Text 3's data directory

\* To install tools conveniently on Windows, you can use [scoop](http://scoop.sh/).

More on ST3's data path, [here](http://docs.sublimetext.info/en/latest/basic_concepts.html#the-data-directory).

### Building

To get a working build of `fsautocomplete.exe` (copied from the emacs plugin):

    ./bin/GetDependencies.ps1

To publish a new version of the plugin locally:

    ./bin/Build.ps1