Bump to version 1.2.0

Version 1.2.0 adds the following features:

* Obey I3SOCK environment variable
* Add Con::find_fullscreen()
* Added properties: `scratchpad_state`, `window_role`
* Con::find_marked() - make pattern optional

And the following bugfixes:

* Fix crash on `barconfig_update` event
* Use underscores to subscribe to `barconfig_update` event
* Correctly put floating nodes in the `floating_nodes` list of the Con

setup.py

@@ -8,7 +8,7 @@
 
 setup(
     name='i3ipc',
-    version='1.1.6',
+    version='1.2.0',
     description='An improved Python library for i3wm extensions',
     long_description=long_description,
     url='https://github.com/acrisci/i3ipc-python',