Warn applications about deprecated methods

[Androbin]

Fixes #146
@non-Jedi /cc
Signed-off-by: Robin Richtsfeld robin.richtsfeld@gmail.com

[non-Jedi]

LGTM. Thanks! (merged into master)

[ghost]

I have some comments though.

• Typo in https://github.com/Androbin/matrix-python-sdk/blob/99002f315425435fa84660ae391117dbdf805c2d/matrix_client/api.py#L197
• This warning in listen_for_events recommends to use _sync. However, starting your method name with an underscore is a common convention in Python to signal that this method is not part of the official API.

Other than that, looking good.

[ghost]

Oh, and to head off the question you will undoubtedly have: I would just drop the recommendation, but maybe @non-Jedi has something to say about that as well. The API is still beta and this is one of those places where it shines through.

[non-Jedi]

Off the top of my head, it seems like we should just expose _sync as sync. Doesn't seem like something we necessarily need to put a ton of machinery in front of.

[ghost]

@Half-Shot: You have written a lot of this stuff and seem to have had a plan for deprecating initialsync. What do you think?