Main changes:
* Use gulpfile now (build was getting way too disorganized with custom
tasks; gulpfiles are much easier to build clean custom tasks with than
Grunt.
* View README#Development for updated commands
* Docs written for ionContent, ionHeaderBar, ionInfiniteScroll.
* Docs are pushed to ajoslin's fork of ionic-site until they reach a
* point where they can be published.
**TODO, In Order of Priority**
1. Finish writing source-documentation for all existing components
2. Add multiple versions of docs (one per release & nightly, latest
stable release docs being shown by default)
3. Add examples generation
4. Add searchbar to docs
Adds new '$ionicBind' service, which takes an object containing
binding definitions (similar to angular directive isolate scope
definition). Allows binding of any directive attribute & expressions
from a scope, letting us do normal attribute -> scope binding
without having to create isolate scopes.
Closes#555. Closes#669
