Add a timeout state to the call model and don't close the window on timeout, but still send hangup to the peer
Add strings and button for a call establishment being timed out and display correctly.
Make call again work; only clear current conversation when the conversation window closes.
When terminating a media call, terminate the local streams so that the devices are released
Remove old timeout notification code
Add functional tests for call timeout handling
Fix minor review comments
Merge with master
Use a more specific send-timeout event for timeouts rather than send-hangup
Merge pull request #179 from Standard8/call_timeout_display

Add display for when a call hasn't been answered