Add sensible defaults for LOCAL 'production' env

* Use gems 'figaro' and 'wannabe_bool' for setting ENV variables from a file (config/application.yml)
* Change 'config/environments/production.rb' to include an environment variable that swithces on/off if assets will be served from Rails or not.
* Create a sample file 'config/application.example.yml' for easy reference
* Create a simple rake task 'rake dev:prepare:production_local' for automatically generate an application.yml file