Several changes to allow for easier Integrations from others.

* getFullUserData now accepts a limit of -1 which will retrieve all of the users, but you only see what you have permission to.
* processWebhookMessage now accepts a roomId for rooms or user, that way integrations don't have to know the name of the channel.
* Fixed the chat.postMessage being broke for messages that contain more than channel and text...whoops!