Fix Mongoid documentation link

URL was moved over time, new official link is this one according to https://rubygems.org/gems/mongoid
Replace named controller name in path with mapping path. Fixes #772
It was okay.
Merge pull request #1001 from ujifgc/fix772

Replace named controller name in path with mapping path. Fixes #772
Fix ruby 1.8.7
Merge pull request #998 from ujifgc/master

Improvement of Padrino's load speed
Merge pull request #999 from hooktstudios/mongoid-doc-link

Fix Mongoid documentation link
Merge remote-tracking branch 'origin/master' into lazy-mail-without-autoload

Conflicts:
	padrino-mailer/lib/padrino-mailer.rb