Add 'is_class' shim
Always use c++11 compiler, but use libstdc++ if not USE_LIBCXX
Removed std::unordered_set::reserve calls

This isn't supported in libstdc++, and is just an optimization
Correcting linker flag adjustment statement
Remove commented out code
Use right library with USE_LIBCXX with xcode
Add empty tuple hash test
Merge pull request #176 from leapmotion/fix-libstdc++

Add general fixes to libstdc++ compilation