tests: don't use github

mono 4.8 on mac simply cannot cope with TLS 1.2; newer versions are not compatible with our travis ci setup.  give up and just use bitbucket.

Author: ethomson

LibGit2Sharp.Tests/SmartSubtransportFixture.cs

@@ -19,8 +19,8 @@ public class SmartSubtransportFixture : BaseFixture
             (sender, certificate, chain, errors) => { return true; };
 
         [Theory]
-        [InlineData("http", "http://github.com/libgit2/TestGitRepository")]
-        [InlineData("https", "https://github.com/libgit2/TestGitRepository")]
+        [InlineData("http", "http://bitbucket.org/edwardthomson/TestGitRepository/")]
+        [InlineData("https", "https://bitbucket.org/edwardthomson/TestGitRepository/")]
         public void CustomSmartSubtransportTest(string scheme, string url)
         {
             string remoteName = "testRemote";