Use request package, add digestAuth handling

Two commits here.  

The first just switches to using request instead of building your own hash.  That's all good.  Tests updated and passing.

The second updates `auth` to add a `digest` flag.  

Good news, bad news.  For whatever reason I can't get digestAuth to work vs httpbin.  It works fine against my own servers running digestAuth.  I've included a test vs httpbin but commented it out as it fails.  I understand if you rather not merge the 2nd commit.  Unfortunately I'm at a point where I have it working and need to get moving with it.  I'm happy working with my branch if need be.