Implemented IUserEmailsClient GetAll and Add methods

Did not implement the Delete method as it is a DELETE that sends a request body.
http://developer.github.com/v3/users/emails/#delete-email-addresses

Not unheard of but still rather unorthodox especially since the body identified the resources to delete. So maybe it's time to start a lobbying group for that as well? If it's not something that's likely to change I'll go ahead and add the required infrastructure methods to handle deletes with a body, but would at least want to check first.

cc @pengwynn
Because you seem to be one of the people to call on for all things GitHub API