Major Changes

Adds: support for multiple variations rather than one thumbnail size.
Sizes can be produces by passing a variation attribute:
`StdImageField(upload_to=‘’, variations={’thumbnail’:(300, 200, True)}`
Updates Tests
fixes variation issues
fixes: variation dictionary issue
fixes: legacy issues
updates: readme, reverts: setup.py
Merge pull request #24 from codingjoe/patch-1

Major recoding