[WIP] Version 2.0

[WIP] 2.0
===
- [x] Support hybrid sign-in flow #13 
- [x] Conform to rubocop
- [x] Support for Ruby 2.0 & 2.1
- [x] Ensure it works for Rails 4 & 4.1
- [x] Squash existing bugs
- [x] Research possible api interaction (possibly seperate gem) #17