initial presence implementation

Signed-off-by: Robert Marklund <robbelibobban@gmail.com>
add setmood and disconnect to client

Signed-off-by: Robert Marklund <robbelibobban@gmail.com>
Merge branch 'trollkarlen-master'
Fix parse_sid_response tests
Remove unimplemented user methods
Remove automatic presence changes for now
Allow event.Event observers to be coroutines

Function observers continue to work as before, but now coroutine
observers can be used. This requires Event.fire to be a coroutine.
Implement Client.set_active()

If there is an active client, notifications are inhibited on other
clients. In other words, now your phone won't buzz constantly while you
chat with someone using hangups.
Move UI modules into a subpackage
Add "projects using hangups" section to readme
Update the readme description
Move setactiveclient into section for used methods
Add some notes about setpresence
Add QHangups link to readme