Reorganize
Merge pull request #9 from nathancahill/reorganize

Organizing __init__.py
Rename collection.py to collections.py for consistency.
Fix import of collections.py.
PEP8
Add group_by() and index_by()
Import Iterable from collections.
Add absolute_import to all files.
Add FIXME comments to cicular import issues.
Remove extraneous lambda usage.
Merge pull request #10 from nathancahill/functions

Add group_by() and index_by()
Merge branch 'master' of github.com:dgilland/pydash
PEP8
Pylint