Added endpoints and big changes to the WordPress plugin

Added ability to specify an endpoint via $.tweetspan('endpoint', url) so that an intermediary endpoint can be used, to provide authenticated calls to the Twitter API

Also updated the plugin to allow specification of consumer and token key and secret pairs, and the ability to set the endpoint should a third-party service be preferable.
Merge branch 'master' of https://github.com/substrakt/jquery.tweetspan

Conflicts:
	jquery.tweetspan.js
	jquery.tweetspan.min.js