Fix #875 and allow closed rooms to have their tab closed.
Merge pull request #877 from cmaish/master

Allow leavecommand to run on closed rooms (allow closing the tab of closed rooms)
Improve behavior around closed rooms
Add ChatRoom.EnsureOpen extension method
Merge pull request #878 from cmaish/improve-closed-rooms

Improve consistency of behavior around closed rooms
Merge branch 'dev' of https://github.com/JabbR/JabbR into dev