Several modifications to google calendar widget

* updated YhoWX and base.py for threading

* isolated run(FLOW, storage) in a separate thread, so that it
doesn't block qtile during the authentication process. This required removing
one line from the oauth2client.tools module, specifically storage.put(), as
that line was not thread-safe. The revised module is included in the
qtile/libqtile directory, and is called custom_tools.py. As a result of this
modification, we have to remember to storage.put() our credentials ourselves in
the main qtile thread.

* added markup and clickability to GC widget