uix:RstDoc add background_color property for consistancy with other
widgets
Set ListItemButton background_color. Fix #1303.
Add warning about ListItemButton gotcha.
Add a file_path argument to UrlRequest.

Write the result of a request to the given file_path.
Remember to close open_file when finished.
Use with statement when writing to file_path.
core:EventDispatcher. Intruduce `bound_events` method that returns a
dict of properties and events of the Widget along with a list of methods
that are bound to the property/event.
uix:TextInput: fix crash when copy/paste bubble is called on long_touch
being the first touch in the TextInput.
core:events rename bound_events to `get_property_observers` and return
only the observers for the property name passed.
core:Events `events` method for returning a list of events of a widget
core.audio: use futur android.mixer instead of android_mixer (fallback to android_mixer right now, in case of.)
example: new example to demonstrate how to use startActivityForResult, and how to get the result with python-for-android android.activity module.
example: add takepicture android.txt + compilation line
docs: kivy dev with P4A_kivy_DIR
example: rework compass example to work with python-for-android, and remove all broken code.
audio: fix volume property that wasnt working. closes #1311, closes #1269
audio: force volume before playing.
urllib: fix urllib handeling in python 2 and 3 closes #1286
animation: fix leak cause of new cancel() that doesnt release the widget reference in Sequence and Parallel animation classes
Merge pull request #1316 from kivy/py2_urllib

urllib: fix urllib handeling in python 2 and 3 closes #1286