Fix fake submodule URL that libgit2 rejects

Author: jspahrsummers

ObjectiveGitTests/GTSubmoduleSpec.m

@@ -61,7 +61,7 @@
 });
 
 qck_it(@"should write to the parent .git/config", ^{
-	NSString *testURLString = @"fake_url";
+	NSString *testURLString = @"git://fake_url";
 
 	GTSubmodule *submodule = [repo submoduleWithName:@"Test_App" error:NULL];
 	expect(submodule).notTo(beNil());