Add new functions to Twitter class allowing to implement
'Sign in with Twitter' option. Also allow the use of
multiple tokens with the library.
Update README.md file with 'Sign in with Twitter' example.
Add Twitter login URLs to config file.
Replace call to the parent's function to reconfigure Twitter class with Twitter's set_new_config.
This allows the getAccessToken function to replace the request token
with the user's token, which should be used from now on on all the calls.
Remove references to ->http_code from the code.
Fix an issue on the example.
The call to request the token doesn't work when access_token and secret
have values defined on the config file. Now it makes sure to overwrite those
values in case they exist.
Merge pull request #36 from j3j5/master

Add functions to Twitter class to be able to authenticate new users