platform-client should maintain the users token

@jh-bate @nicolashery 

Platform client should be maintaining the user token rather than requiring anybody and everybody who uses platform-client to implement the same logic of keeping their token up-to-date.

This PR changes all of the methods to not take a token anymore and adds the logic to maintain the token in the client.  Tests have been adjusted and all still pass.  This needs to be done now before we go and write even more code in here that will just need to be changed later.

Btw, there were some whitespace formatting changes in here as well, so you might want to look at the diffs with the `w=1` query parameter.