v0.8.3 release notes & version update

[jackiekazil]

This is just an update of the history file and version number on Mesa.
Reviewing all the things that were done since the last release made me smile. :-) There are so many awesome things that happened. Thank you everyone your contributions!!

Can someone do a review of the history file and make sure that I haven't missed anything that changed since v0.8.2 (Gila Bend)?

Everything that is a part of this release has been tagged with the Hayden milestone.
https://github.com/projectmesa/mesa/milestone/16

[coveralls]

Coverage remained the same at 81.287% when pulling 93760f1 on release into d147ff6 on master.

[coveralls]

Coverage remained the same at 81.287% when pulling 93760f1 on release into d147ff6 on master.

[dmasad]

I've merged in a few outstanding PRs today, so we should probably update the history to match.

[jackiekazil]

@dmasad done.... can I get a thumbs up from you or someone else?

[coveralls]

Coverage decreased (-0.4%) to 80.841% when pulling e6b2ab3 on release into d147ff6 on master.

[coveralls]

Coverage decreased (-0.4%) to 80.841% when pulling 60fb783 on release into d147ff6 on master.

[coveralls]

Coverage decreased (-0.3%) to 81.019% when pulling 3c8b521 on release into d147ff6 on master.

[dmasad]

LGTM

[jackiekazil]

This was pushed to PYPI - https://pypi.python.org/pypi/Mesa/0.8.3