Create URI::GlobalID scheme

Addresses https://github.com/rails/globalid/issues/6
It's basically used in the [`component` class method](https://github.com/ruby/ruby/blob/trunk/lib/uri/generic.rb#L54-L56) that's used by the [`component` instance method](https://github.com/ruby/ruby/blob/trunk/lib/uri/generic.rb#L309-L311) which is basically used in other instance methods to validate and select specific components.