* Updating subprocess.pyi to support python 3.5
Also added DEVNULL which was added in 3.3
* Incorrectly checked sys.version_info
* Addressed travis build failures
Forgot that __init__ should return None and also forgot "self" on a method. Like a dummy.
* subprocess.CalledProcessError output argument is optional.
* subprocess.CalledProcessError takes stderr argument in python3.
* subprocess: Fix type for command in call() and friends.
The stubs didn't correctly support the fact that you can pass a string
as well as a sequence of strings.
