Add Contributor Only Pet Choice

This PR https://github.com/HabitRPG/habitrpg-shared/pull/33 should completed before this one.
Update pets.jade
Rare Pets Layout

Shows rare pets header always.

Shows golden missing rare pet graphic if Hydra not obtained with link to how to obtain it.
contrib: add Admin page to update contributor status. Start migrating from User.backer => User.contributor
contrib: equipped functions to use habitrpg-shared@959024d
Merge remote-tracking branch 'Shaners/patch-3' into contrib

Conflicts:
	views/options/pets.jade
contrib: award profile Dragon-Hydra if admin sets level >= 6
contrib: add name-tag colors based on contributor level
contrib: add migration to help me start porting existing contribs
contrib: show profile._id in modal so admins can assign contrib status
contrib: add contributor achievement modal
Merge branch 'contrib' into develop