make dropbox files synclet page externally
Merge pull request #834 from Singly/dropbox-paging

make dropbox files synclet page externally
adding earliest map for facebook photos
only set the cursor if it has changed

this was verbally +1ed by @kristjan
duplicate the at to the normalized earliest value for photos too
Implement `earliest` for flickr
Implement `earliest` for shutterfly
Implement `earliest` for picasa
Implement `earliest` for gplus photos
make shutterfly earliest use some optional older timestamps
fix the fixture
Merge pull request #836 from Singly/photos-map-earliest

adding earliest map normalization for all photo services