emulating old behavior, non success http statuses return an error
Revert "Merge pull request #45 from yahoo/xhr"

This reverts commit bb32225bc6733763f1e8bf7b80a48746be23b141, reversing
changes made to eaaf51d4acd5e462b2105c53bfeb377c85e590a6.

Conflicts:
	libs/util/http.client.js
Set responseText on the response object to emulate old XHR behavior
Add statusCode to error object
Remove unused error and response modification methods
Use doXhr for retry
Merge pull request #48 from yahoo/not-good-err

Fix XHR response changes