Mac OS X setup adaptation

Tested on OS X 10.8.3, Python 2.7.5, hdf5 1.8.11 (homebrew). I didn't test with llvm-gcc, it could work.

I think the lightweight commit is self-explanatory. For the record here are my bash commands:

    # using homebrew http://mxcl.github.io/homebrew/
    brew install --enable-cxx hdf5 
    # enable-cxx: I want the C++ bindings for myself, not tested without
    git clone git@github.com:SnippyHolloW/h5py.git
    cd h5py/
    virtualenv --system-site-packages .
    source bin/activate
    cd h5py/
    python api_gen.py
    cd ..
    export CC=gcc-4.8
    python setup.py build
    python setup.py install

`import h5py` works. And finally:

    (h5py)~/labs/h5py $ python setup.py test
    Autodetected HDF5 version 1.8.11
    running test
    running build_py
    running build_ext
    skipping 'h5py/defs.c' Cython extension (up-to-date)
    skipping 'h5py/_errors.c' Cython extension (up-to-date)
    skipping 'h5py/_objects.c' Cython extension (up-to-date)
    skipping 'h5py/_proxy.c' Cython extension (up-to-date)
    skipping 'h5py/h5fd.c' Cython extension (up-to-date)
    skipping 'h5py/h5z.c' Cython extension (up-to-date)
    skipping 'h5py/h5.c' Cython extension (up-to-date)
    skipping 'h5py/h5i.c' Cython extension (up-to-date)
    skipping 'h5py/h5r.c' Cython extension (up-to-date)
    skipping 'h5py/utils.c' Cython extension (up-to-date)
    skipping 'h5py/_conv.c' Cython extension (up-to-date)
    skipping 'h5py/h5t.c' Cython extension (up-to-date)
    skipping 'h5py/h5s.c' Cython extension (up-to-date)
    skipping 'h5py/h5p.c' Cython extension (up-to-date)
    skipping 'h5py/h5d.c' Cython extension (up-to-date)
    skipping 'h5py/h5a.c' Cython extension (up-to-date)
    skipping 'h5py/h5f.c' Cython extension (up-to-date)
    skipping 'h5py/h5g.c' Cython extension (up-to-date)
    skipping 'h5py/h5l.c' Cython extension (up-to-date)
    skipping 'h5py/h5o.c' Cython extension (up-to-date)
    skipping 'h5py/h5ds.c' Cython extension (up-to-date)
    ....................................................................................................x..........................s........ss................................................................................sss.................................................
    ----------------------------------------------------------------------
    Ran 270 tests in 0.274s

    OK (skipped=6, expected failures=1)