Fixes LP-1403596

  OS X (darwin) uses stat.Ctimespec not stat.Ctim

  updated per review comments
Merge pull request #1337 from johnweldon/lp-1403596

Fixes LP-1403596

  OS X (darwin) uses `stat.Ctimespec` not `stat.Ctim`

(Review request: http://reviews.vapour.ws/r/655/)