Modified add_qiime_labels.py script to use a standard metadata mapping file instead of custom mapping file to be more intuitive to use with the rest of QIIME.  Updated unit tests.
Added changes to add_qiime_labels script/library to Changelog
Merge branch 'add_qiime_labels' of github.com:walterst/qiime

Conflicts:
	ChangeLog.md
Merge pull request #577 from walterst/add_qiime_labels

Modified add_qiime_labels.py script to use a standard metadata mapping f...