Engage discussion with Astropy.

[Carreau]

Talked with @astrofrog a bit today.
Opening issue to track.

[astrofrog]

There was some initial (positive) discussion about signing the python 3 statement a few weeks ago: https://groups.google.com/forum/#!topic/astropy-dev/0pumTIoqV5Q - before we do vote on signing this, we want to come up with a concrete plan of action for future releases.

[takluyver]

Closed by #47