Release 0.2.2

[ujh]

I ran tests on 13x13 with the empty are prior turned on, turned off, and set to 20. All were about the same (8-10 wins in 100 games) so I decided to turn the prior on for now and set it a bit higher to avoid plays on the first two lines. I'm not even sure if that makes sense or not.

Before merging this, I'll update the change log and I'll run benchmarks (again).

[coveralls]

Coverage increased (+0.35%) to 83.79% when pulling 78009e5 on release-0.2.2 into 29a0a06 on master.

[coveralls]

Coverage increased (+3.59%) to 87.02% when pulling 008884d on release-0.2.2 into 29a0a06 on master.

[coveralls]

Coverage decreased (-11.02%) to 72.414% when pulling c30288d on release-0.2.2 into 29a0a06 on master.