Getting setup ready for a release

MANIFEST.in doesn't control what gets installed/copied to the install location, only what ends up in the tar.gz (why would you want them to be different?).

I've tested this by
- getting a clean copy of the repo: `https://github.com/biocore/scikit-bio.git`
- Running `python setup.py sdist` to create the `tar.gz`
- Making a clean environment with pip, nose, numpy, scipy, matplotlib, pandas and future (one for Py 2.7 and another for 3.4)
- Moving to a different directory. (is this necessary? Just wanted to make sure that nothing was happening with the actual source code, everything was going through the `.tar.gz`)
- Running `pip install path/to/....tar.gz` (extracting it before isn't necessary)
- Running `nosetests skbio` to run its tests. Everything passes, including doctests in Py 2.7.

It should close #369.