Create URI::GlobalID scheme

Addresses https://github.com/rails/globalid/issues/6
You are write @kaspth, my explanation was incorrect. `URI::InvalidURIError` is raised by [`URI::Generic`](https://github.com/ruby/ruby/blob/trunk/lib/uri/generic.rb#L586-L598) when the value for `host` is invalid, that's why we need to rescue from both exceptions here.