Setup config slice to return a 'slice_success' object from GET against its RESTful API
Adds code that handles non-JSON responses from the Hanlon RESTful API.
These changes are critical for ensuring that the same error handling code is used
with *all* responses from the Hanlon RESTful API (including the text response from
the /config/ipxe endpoint).
Merge pull request #96 from tjmcs/tb/return-config-as-object

Merged.  Thanks, everyone!