add pg gem for production heroku
set config.assets.initialize_on_precompile = false in production for heroku
Revert "set config.assets.initialize_on_precompile = false in production for heroku"

This reverts commit c1a86a838479a66160d5a11b2fa5769916b625f8.
precompile production assets for heroku

via RAILS_ENV=production bundle exec rake assets:precompile
add rails_12factor to help with compiling assets on heroku

http://stackoverflow.com/questions/15354539/heroku-does-not-compile-files-under-assets-piplines-in-rails-4
serve static assets in production