Some fixes

* change `xcb` to `xcffib`

* allow for running with 3.2 by adding a compatibility function for unicode literals

* since `ffi.verify()` was dropped from pangocffi (though we may want to bring it back if we can get cairocffi to use `ffi.verify()`), drop the `ext_modules` from setup.py

* fix an integer division used for the systray icon (still doesn't fix displaying it for me, tho)