Include Feathers client core for universal Feathers applications #191
Description
As mentioned by @ahdinosaur in #156, what is currently in feathers-client can actually be moved into the main repository and the respective transports. Using the browser field, this will allow for a fully isomorphic Feathers that can be used the same way on the client and the server, including feathers-hooks (related issue feathersjs-ecosystem/client#20).