Provide better defaults when linking client, and managing credentials.

Don't require the user to provide all the functions when linking client.  Default using nops.

In the credentials, allow null to signify not to use a cache.
Switch order of err and data on get callback.  General clean up.
Reverse the order of error and value in get callbacks.
Clean up getJSON.
Successfully compiling files in the root directory.  lots of unnecessary log messages.
Add error return and status on error for delta.