Added tests around specified 'simple' behavior (which fail)
Make simple option true by default as specified in README

Simple was undefined (falsy) unless specified explicitly
Fix logic error in request handler

Was rejecting in simple mode if the response was a valid status code,
instead of when it wasn't.
Merge pull request #3 from FellowMD/fix

flush out tests, allow simple behavior by default, and fix logic for checking default status codes