Modified supervised_learning to accepted an input directory, can produce individual results file or a collated results file if -w is passed
Updated usage examples and script description
Addressed wvwdt1 style suggestions
Addressed ElDeveloper's style suggestions
Merge branch 'master' of git://github.com/qiime/qiime into supervised_learning
Updated ChangeLog.md with supervised_learning mods
Merge pull request #807 from lkursell/supervised_learning

supervised_learning.py handles input directories