Removed flag in setup.py for clang compatibility

Fixes error when building with clang (Apple LLVM version 5.1 (clang-503.0.40) (based on LLVM 3.4svn))

Error shown below:

clang -fno-strict-aliasing -fno-common -dynamic -I/usr/local/include -I/usr/local/opt/sqlite/include -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/usr/local/lib/python2.7/site-packages/numpy/core/include -I/usr/local/lib/python2.7/site-packages/numpy/numarray/include -I/usr/local/Cellar/python/2.7.6_1/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c external/pysoundtouch14/libsoundtouch/AAFilter.cpp -o build/temp.macosx-10.8-x86_64-2.7/external/pysoundtouch14/libsoundtouch/AAFilter.o -fcheck-new -O3 -Wno-unused

clang: error: unknown argument: '-fcheck-new' [-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 'clang' failed with exit status 1