update lita-github to v0.1.0 and Lita ~> 4.0

This is the `0.1.0` release for `lita-github`. The only changes from `0.0.16` are as follows:

* Bump required Lita version to `~> 4.0`, update specs to use new route matcher, and disable Lita v3.0 compatability mode.
* Bump Rubocop version to `0.28.0` and fix angry police.

There have been no logic changes from `0.0.16` to `0.1.0`.
Merge pull request #31 from PagerDuty/lita-4.0_and_0.1.0

update lita-github to v0.1.0 and Lita ~> 4.0