Add LineItem to xeroid/objects.rb auto loading
Rename Xeroid::Clients to Xeroid::Auth, since that's much more accurate
Make Xeroid::Auth::Private autoloadable
Add Xeroid::Client object to create Endpoint objects for actually making API calls
Pass the Endpoint path to Endpoint.new
Add the simplest possible way to do make-a-signed-http-request for real

* Response not super helpful here.