removed empty parameters form query string in OauthPlugin
Cleaning up OauthPlugin
Fix Date vs. Last-Modified header issue in DefaultRevalidation.php.
Add fallback to Date if Last-Modified is not present.
Adding support for oauth_callback parameter.
Adding callback parameter to constructor docblock.
Adding the ability to PURGE requests from the cache. Addresses #241.
Loosening check for oauth_token. Closes #287.
Moved decision of whether to sign post fields to a function.

Some non-conformant APIs that have incorrect implementations of Oauth may require this method to be overridden.
Changed tab to space.