Hard fork to the new API

This is a hard fork that eliminates support for the old [/v1/ API](http://doc.intercom.io/api/v1/) which was deprecated on 6/17/2014. It also adds support for new features, such as segments and companies. Conversation support is included in the current API (not /v1/), but have not been implemented yet (it would be easy enough to do so). Readme has been updated appropriately to reflect these changes.