use git for gemspec, fixes #327
use devise_parameter_sanitizer, fixes #326 supporting strong parameters
Sync up with Devise 3 dependencies

- allow Rails 4
- require at least Rails 3.2
- skip railties dependency that Devise already has
Merge pull request #329 from turadg/patch-1

Sync up with Devise 3 dependencies
add note about config.scoped_views, fixes  #330