Port coordinates parser to skbio's parser

NOT READY FOR MERGE

I'm not completely sure if I've updated .travis.yml correctly, so let travis run the tests. Also, we're expecting the tests to fail on numpy 1.8, but on travis is easier to test al possible combinations (testing matrix).

Fixes #260

- Adds scikit-bio as a dependency for emperor.
- Removes the `pycogent_backports` folder as procrustes is already on scikit-bio.
- Updates setup.py to require numpy >= 1.7 (the versions supported by scikit-bio)
- Updates .travis.yml to test against numpy 1.7 and 1.8