Fix: Ensure compatibility with OAuth2 gem

The OAuth2 gem uses the parameter name :headers while rapidash was
using :header, :headers is now being used.
Version Bump to 0.1.2
Update README to include rapidash rails demo
Merge remote-tracking branch 'origin/development'

Conflicts:
	lib/rapidash/http_client.rb
Fix: Ensure the body is set to JSON correctly

When HTTP is used, it appears that the JSON is encoded at the point
of request.  This is not the case with OAuth.

The OAuth client now json encodes the body at the point of request.
Version bump to 0.2.0