Remove s.framework = "XCTest" from the podspec

I was having issues building, since I'm not using XCTest yet. I was able to build and use OCMock 3.x locally just fine without linking XCTest. This should also fix #149.
Merge remote-tracking branch 'upstream/master'
Merge pull request #154 from bashery/master

Remove s.framework = "XCTest" from the podspec