Add better_errors gem. Add meta_request gem for Chrome rails panel

http://railscasts.com/episodes/402-better-errors-railspanel
Important changes in routes.rb:
  - Add prefix on default locale, but maintain compatibility with old routes.
  - All routes related to habitapedia starts with "/habitapedia/..."
Language selector
travis.yml. Travis only builds the master branch
Los modelos con FrienlyId usan el módulo History de FriendlyId.
Aquellos que además tienen traducciones usan el módulo SimpleI18n de FriendlyId
Adaptar la base de datos y los modelos para trabajar con Globalize3 y FriendlyId
Populate friendly_id history and translate some routes to :ca
Redirects with correct slugs in the url when changing locale