Updating README
Adding support for refresh token.
Adding function to validate state and thus reducing some code duplication.
Removing unused imports.
Fields to retrieve are now configurable.
Receiving a JSON instead of an XML.
Merge branch 'master' of https://github.com/ghostm/lift-omniauth
Use the function to test state token.
Cleaning up the code.
Making linkedin fields static since currently it is not configurable.
Merge pull request #30 from ggarciajr/master

adding support for refresh token and some code improvements.