Fix unit test discovery of test assets

Author: AArnott

LibGit2Sharp.Tests/TestHelpers/BaseFixture.cs

@@ -61,7 +61,7 @@ private static void SetUpTestEnvironment()
 
             string initialAssemblyParentFolder = Directory.GetParent(new Uri(typeof(BaseFixture).Assembly.EscapedCodeBase).LocalPath).FullName;
 
-            const string sourceRelativePath = @"../../../LibGit2Sharp.Tests/Resources";
+            const string sourceRelativePath = @"../../../../LibGit2Sharp.Tests/Resources";
             ResourcesDirectory = new DirectoryInfo(Path.Combine(initialAssemblyParentFolder, sourceRelativePath));
 
             // Setup standard paths to our test repositories