Updating the Processing column

Should be directly coupled to processing of the attachment
Added failing spec for double save problem
Fixing a pending spec

Hopefully fixes https://github.com/jrgifford/delayed_paperclip/issues/52

Thanks to @pluff (https://github.com/jrgifford/delayed_paperclip/pull/80) and @evanbeard (https://github.com/jrgifford/delayed_paperclip/pull/54) for narrowing down this issue.