Switch to postgresql db rather than sqlite3.

Switch the db to use postgres rather than sqlite. Found and fix bug in
the parent form.
Add Admin Section

Added admin signing so owner can edit the labs and litters and
approve/disapprove potential clients. Editing pages are inaccessible
unless the user is logged in and redirect to the homepage if they try
to get there. When logged in, tools link and logout link are displayed
in upper right.

Updated labrador new/edit pages.
Updating litter/puppy_parents admin pages

Updated the editing pages for litters and puppy parents. They are only
accessible when logged in.

Updated Gemfile for Heroku