Pretty big change. Things now pass up errors that can be handled by the
caller. This brought about a lot of change. Errors attempt to be
descriptive of where they came from and notify user of the api what
potentailly caused the error. Also renamed go-halo5-api.go to a more
suitable name, http.go. This might change in the future if we implement
the http.Client interface
Lots of tests have been added to the main.go file. Several of the functions return structs now instead of json strings. I've added the initial structs for the remaining functions.