Scribe Java 4.0.0 update

[gcrick]

Updated code to work with Scribe Java 4.0.0 and adjusted tests (all pass now). Updated plugin version to 4.0.0 due to breaking changes:

• All Scribe classes have been moved to new packages. This means most clients will have to change provider configuration. For example, org.scribe.builder.api.FacebookApi is now com.github.scribejava.apis.FacebookApi.
• Some method signatures in OauthService.groovy have changed to take into account the differences between OAuth 1 and OAuth 2 in the new Scribe Java. Also, some of the dynamic methods now dispatch to one version or another based on the number of arguments received.
• Clients that make use of Scribe Java directly might have to add the API dependency explicitly: compile 'com.github.scribejava:scribejava-apis:4.0.0'

The changes were made somewhat blindly, without a deep understanding of OAuth - the minimum to make the tests pass and enable login with Facebook and Google. Some parts of the code are questionable. For example, OAuth2 does not use a RequestToken now, yet the plugin expects to find a RequestToken in the session in both cases and uses EMPTY_TOKEN for OAuth 2. Since Token is abstract in the new library, the value of EMPTY_TOKEN has been changed to an OAuth2AccessToken, which makes no sense.

[antony]

This is great @gcrick - thank you for your stellar efforts.

I'm intrigued that scribe have done a u-turn on the Oauth2 decision, after threatening to remove it.

I'll endeavour to get this merged in ASAP.