Add original code written by @jansuategui

Credit goes to @jansuategui for writing this code. Code was provided to me by @cleme.

Tested it against a couple of datasets and it appears to be working with biom-format 1.2.0, PyCogent 1.5.3, numpy 1.5.1, and QIIME 1.7.0-dev, master@36db13d. Unit tests pass after fixing an import error.

Removed csmat.py as it can just be imported from the biom-format package.
Merge pull request #1 from jrrideout/initial

Add original code written by @jansuategui
Reorganize files

Tests go into test directory, library code goes into ```sparse_unifrac``` module, and script goes into scripts/.

Tests are now runnable via nose:

    nosetests tests
Remove QIIME dependency
Update README.md with unit test instructions
Merge pull request #2 from jrrideout/reorganization

Codebase reorganization