Defaulting `:no_local` to `false`

[sshaw]

Currently the default configuration is surprising: validates :my_column, :url => true accepts http and https schemes but it accepts invalid "non-local" domains: https://foo-hoo. Feels like more people what want the valid public domain case over this. To do this one has to add :no_local: validates :my_column, :url => { :no_local => true }.

This gets to be a bit more user-unfriendly when there are several models with URL validation as one cannot set :no_local => true as a global default.

See also #59