Some minor tweaks

Fixed problems:
* html5shiv-printshiv.js added to assets precompile

Alterations:
* removed heroku gem in favor of heroku toolbelt https://toolbelt.heroku.com/
* added admin_users to active admin pannel. Enabling the management of admin_users from the start of the project.
* datepicker now has a translation to portuguese, which is now default (hardcoded for now)