Create URI::GlobalID scheme

Addresses https://github.com/rails/globalid/issues/6
Because of the behaviour we expect this class to have we need to set `arg[10]` value as `true` unless it has already been set to `true` or `false`. In other words we need `arg_check` to default to `true` for `URI::GlobalID` before calling `URI::Generic` constructor which defaults to `false`.