* test suite, including request strategy test suite
* IE10 should now behave as a CORS supported XMLHttpRequest browser,
as it is
* running tests on many browsers, using saucelabs
* refactor around `_makeXmlHttpRequestByHost` and
`_makeJsonpRequestByHost`
* remove unused opts.callback(retry, success, obj, message) in all
make..Request functions
* FIX: do not retry with JSONP when statusCode is 4xx