Fix Markdown test

The markdown api adds a trailing newline if there isn't already one. It
also converts \r\n to \n.
Fixed some async void tests

These tests weren't getting run.
Stop requesting ALL public gists

We don't need this in our integration tests.
Ensure no async void methods

Added self tests to find async void methods. It found some cases where
we passed an async lambda to a method that did not accept Action<Task>
or Func<Task>. I fixed those tests.
Merge pull request #604 from octokit/haacked/test-fixes

Async Void Test Fixes