Added MANIFEST.in

[ocefpaf]

The source dist for ulmo-0.8.0.tar.gz at PyPI seems to be broken. I added a MANIFEST.in and that will probably fix it.

> pip install ulmo-0.8.0.tar.gz
Processing ./ulmo-0.8.0.tar.gz
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 20, in <module>
      File "/tmp/pip-NYwRgB-build/setup.py", line 39, in <module>
        __version__ = version()
      File "/tmp/pip-NYwRgB-build/setup.py", line 34, in version
        with open(os.path.join(rootpath, "VERSION.txt")) as v:
    IOError: [Errno 2] No such file or directory: '/tmp/pip-NYwRgB-build/VERSION.txt'