0.6.1 Release

Just pushing out a few of the recent accepted PRs, and poking around the testing infrastructure changes...

While evaluating the integration test suite against the new xUnit test runner, I also monitored the network activity in Fiddler. Some integration tests were unnecessarily chatty - for example, fetching all commits for a repository, and some were unnecessarily bound to creating a dummy repository.

I focused on `RepositoryCommitsClientTests` and tuned these for faster feedback. I'll keep an eye on other slow tests as we're pushing out other releases. I'll come back to those other skipped tests as well.

 - [x] version bump
 - [x] release notes
 - [x] publish to MyGet
 - [ ] :shipit: