repo: Change description

[guillermooo]

I think this may be innacurate:

Bundle for using Dart with TextMate or Sublime

I would suggest to change it to something like this:

Sublime Text Dart Package

While some parts may be reused for a TM bundle, I don't think we can mantain versions for both here in this repo.

[guillermooo]

@sethladd I think you or another admin need to decide about this. It's just a minor thing, though.

[sethladd]

Fixed. Thanks for noticing!