ENH: Add functions to summarize metadata stats
DB Modifcations for study creation

- Made two columns nullable in study table (number samples collected/promised)
- Added affiliation column to study_person to reduce likelihood of name
  collisions
Add unique constraint to study_person
Add affiliation property to StudyPerson class

also changes lookups to be based on name/affiliation since that is the unique
constraint
Add affiliation to test db population script
Fix typo in MANIFEST.in
Merge pull request #264 from adamrp/fix_manifest

Fix typo in MANIFEST.in
API: Change the name of the functions
ENH: Cast from defaultdict to dict
ENH/BUG: Change datetime objects to strings
TST: Add corresponding tests for util.py
DOC: Add docstrings for added functions in util.py
Fix tests, add tests for affiliation

Modify study and command tests to expect new affiliation argument
Merge pull request #263 from adamrp/mod_db

DB Modifcations for study creation
STY/ENH: Remove default dict and change names

It was pointed out that defaultdictionaries were not needed and that
some function names were rather confusing.
STY: Change variable names and use viewitems

viewitems is a py2/py3 compatible version of items for dictionaries.
Additionally some of the variable names were changed to be more
descriptive about the data they contain.
Merge pull request #265 from ElDeveloper/metadata-stats

Add metadata wrangling functions to qiita_ware
ENH: Add natsort to setup.py
ENH: Add suggestions as they were requested in CR
Merge branch 'master' of git://github.com/biocore/qiita into metadata-stats