Debugging this problem took quite some time for me. If you faced the following error

clang: error: unknown argument: '-mno-fused-madd' [-Wunused-command-line-argument-hard-error-in-future]

Reason

The Apple LLVM compiler in Xcode 5.1 treats unrecognized command-line options as errors.

Work around

ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future pip install <ur package>

You can read in detail about it here.

http://bruteforce.gr/bypassing-clang-error-unknown-argument.html