Allow access_token to be injected during client configuration
Add WHCC error codes
Refresh access token if expired.

* Adds http methods directly on client.
* Maps and raises error codes.
* Rescues expired token, refresh and retry request.
Change request_access_token to a GET
Use HTTP methods on client.

In order to take advantage of the access token refreshing,
need to use the http methods on the client vs. using the connection
object.