Provide some information about "temp_libs" on Mac OS X when building wheels.

[mforbes]

When building a wheel on the darwin platform, setup.py expects various libraries to be in the non-existent folder temp_libs. It would be helpful to include some information about the intended use.

The following works for me (Mac OS X 12.5.1):

port install portaudio portmidi libsndfile liblo
ln -s /opt/local/lib temp_libs
python setup.py bdist_wheel

Otherwise I get a rather cryptic error message

error: can't copy 'temp_libs/liblo.7.dylib': doesn't exist or not a regular file

(At least it was cryptic until I figured out that setup.py was looking for temp_libs.)

[belangeo]

"temp_libs" is auto-generated by the script I use to create wheels for the supported python versions when I'm preparing a release. I want to change these hard-coded paths in favour of looking into the installation path of brew, which will make building from sources more easier for everyone to handle.