Fixed documention errors in the README.
Changed default catch back to Exception
Extend FacebookRedirectLoginHelper storeState and loadState method

Change $state property visibility to protected in order to use by
getSessionFromRedirect which call loadState method and set $state.
Removed FacebookSDKException from use statements
Merge pull request #5 from SammyK/documentation-fixes

Fixed documentaion errors in the README
Merge pull request #19 from carlsonorozco/master

Change scope on FacebookRedirectLoginHelper state
Use PSR-4 loading instead of classmap