a refactoring version of the scribe oauth library.

[2.0.0]

• FEATURE: a refactoring version of old scribe, rename to OAuth Simple.
• FEATURE: add all signature style support for oauth 2.0.
• FEATURE: add all grant type support for oauth 2.0.
• FEATURE: add username/password and refresh token support for oauth 2.0.
• FEATURE: use new OAuthToken class, add more must be fileds.
• FEATURE: add xauth support for oauth 1.0.
• FEATURE: add http proxy support for request.
• FEATURE: add real and easy to use multipart support for request.
• FEATURE: refactoring request, make it easy to use.
• FIX: fix most bugs for oauth and request.