Fizzy -- Feature Selection

I've added a feature selection extension to QIIME that applies variable selection (based of information-theoretic methods) to a data set stored in a biom file. The class labels are set by pointing to a column in the map file. I have not modified any of the QIIME scripts (only the README.md). The added files are `qiime/fizzy.py`, `scripts/fizzy.py`, `tests/test_fizzy.py`, and the directory `/tests/test_fizzy/`, which contains some scripts for a unit test. The only external dependency should be [PyFeast](https://github.com/mutantturkey/PyFeast).