Remove deprecated `shared_templates_api`

If we're doing a v2, we probably don't need this. It just adds cruft.
Merge branch 'master' into prep-for-v2-release
Remove helpers api.

Helpers are accessible via global context.
Support rails v2.3
Merge remote-tracking branch 'origin/pr/95'
Merge remote-tracking branch 'origin/pr/102'
Update CHANGELOG.