Ensure environment variables are set for clang compiler on os x

[ianvmfarms]

Running pip install -r requirements.txt yields:

cc -fno-strict-aliasing -fno-common -dynamic -arch x86_64 -arch i386 -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -mno-fused-madd -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -fwrapv -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch x86_64 -arch i386 -pipe -I/System/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c /Users/ian/Envs/exepyvenv/build/cython/Cython/Plex/Scanners.c -o build/temp.macosx-10.9-intel-2.7/Users/ian/Envs/exepyvenv/build/cython/Cython/Plex/Scanners.o

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

clang: note: this will be a hard error (cannot be downgraded to a warning) in the future

error: command 'cc' failed with exit status 1

----------------------------------------
Cleaning up...
Command /Users/ian/Envs/exepyvenv/bin/python -c "import setuptools, tokenize;__file__='/Users/ian/Envs/exepyvenv/build/cython/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --record /var/folders/zq/wm6wrrp54lg9knxyzrks0y3c0000gn/T/pip-TwBvWH-record/install-record.txt --single-version-externally-managed --compile --install-headers /Users/ian/Envs/exepyvenv/include/site/python2.7 failed with error code 1 in /Users/ian/Envs/exepyvenv/build/cython
Storing debug log for failure in /Users/ian/.pip/pip.log

To fix just do:

export CFLAGS=-Qunused-arguments
export CPPFLAGS=-Qunused-arguments

As per http://stackoverflow.com/questions/22313407/clang-error-unknown-argument-mno-fused-madd-python-package-installation-fa