Photo Model

This is untested...I need S3 keys (#232) and I need someone to get a post working for either field_reports, or sites with an attached photo. We're going to do something like: http://stackoverflow.com/questions/12549759/carrierwave-programatic-upload/12729297#12729297 (not exactly though)

Fix #52 
Fix #235

FYI, we're using carrierwave and fog for uploads if you're interested in seeing how that works.