upgrade some dependencies

Mainly upgrades rails to 4.1.1 to fix vulnerabilities and locks sass-rails to 4.0.2 to avoid issues with sprites generator

Activerecord-postgis-adapter now creates postgis extensions in the public schema (following the new postgis 2.1 default). After run `rake db:migrate` the _/config/database.yml_ file should be edited to remove `postgis` from `schema_search_path`