fix 'es' subdomain with default site

This fixes the first bug with es.railsbridge.org -- now the default site ("docs") comes up OK inside the "sites/es" subdirectory.

However, there are still some problems... e.g. `http://es.railsbridge.org/es/escoge_tu_sistema_operativo` is failing with `No such file or directory - /app/sites/es/escoge_tu_sistema_operativo/escoge_tu_sistema_operativo`

Also, inside the "codificadas/docs" fork there is a branch named "docs" and a branch named "master". What's the "docs" fork for vs. "master"?