added support for tab dragging onto an open chat window
Merge pull request #146 from n1k0/drag-a-tab

Support for tab dragging onto an open chat window
Change talkilla.call-start to talkilla.conversation-open to better reflect the fact we're opening the conversation window
In the worker, change the concept of currentCall to currentConversation, and refactor the conversation into an object
Fix review comments
Merge pull request #147 from Standard8/conversation_refactor

Refactor some concepts of 'call' to 'conversation' to better reflect the conversation window