jdk path for osx 10.9 fixed

I've fixed an error occurred while installing jpype on Mac OS X 10.9. It's caused when it failed to locate path for jdk and eventually could not find jni.h.
I'm not sure of Mac OS X 10.8 or lower, yet for OS X 10.9, jdk path located in Xcode.app should work. I think 10.10 and higher should work in the same way.