Update gems to rails 4 compatible
Changing some rails 4 config flags
Moped::BSON -> BSON
Update remaning models/controller/tests for rails 4
Remove ruby version from Gemfile

It is not a good idea to have a ruby version on the Gemfile, specially if you are using RVM,
as rvm sets ENV[RUBY_VERSION] using the revision number: ex.: ruby-2.0.0-p247 , which does not work