Push access cleanup

[Aaron Meurer]

Hi everyone.

This is just to inform everyone that I've gone through and removed the
GitHub push access for anyone who hasn't had committed code in the
past year, according to our policy.

This is done for security purposes only. If you had push access before
that was revoked, and you start contributing again, I will be happy to
reinstate it.

If I have been contributing recently and I removed your access on
accident, or if you want to start contributing again, please let me
know and I will reinstate it.

Aaron Meurer

[Aaron Meurer]

I went ahead and wrote this policy down on the wiki
https://github.com/sympy/sympy/wiki/Pushing-patches#push-access-removal-due-to-inactivity,
since it didn't seem to be written down (we have done it before, but
it wasn't written down anywhere other than the mailing list).

Aaron Meurer