Check proxy support

[inclement]

It's not clear how to use a proxy with python-for-android. This should at least be documented, and the feature actually added if it needs some changes.

[Julian-O]

Suggestion: Break this into two parts. If someone with knowhow could put the rough technical details here (in this issue) of how to use a proxy, maybe someone else with writing skills could put the pretty words together for the documentation.