Fixes #100


libffi would not build with xcode 6 because libffi version 3.0.13 uses a iphoneos min version of 4.0 for compiling for the simluator, but it works if you change the iphoneos min version to 6.0. libffi version 3.1(latest) has a iphoneos min version of 5.1.1 and has the same problem. Solution would be to disable compiling for the simulator, or changing the version. I opted for the later, as I am working on ios simulator support.