Some data attributes cleanup
- Rename env on Scope objects to data
- Pass data attributes as kwargs to nested render calls (options['fn']/options['inverse'])
- Pass data attributes as a dictionary to root render call, to avoid name conflicts
- Add a decorator to process data args before passing in to nested render calls
Make data attributes accessible in non-block helpers
- Make `this` variables refer to a Scope
- Use this.context explicitly wherever we need a non-Scope object
- Add comments to render initialization
- Fall back to __getitem__ if Scope context has no `get` method
Update tests for hashes from Handlebars.js
Merge branch 'data-hash'

Conflicts:
	pybars/_compiler.py