Release 2.4.5.2.
Release 2.4.5.2.

Changelog:
 - Merge in upstream #69.
 - Various odds and ends in the readme.

owahab/delayed_paperclip,hewrin/delayed_paperclip,leighhalliday/delayed_paperclip,cgunther/delayed_paperclip,jrgifford/delayed_paperclip,matt0903/delayed_paperclip,tonchidot/delayed_paperclip,ombulabs/delayed_paperclip