fix oauth, slacking nokogiri dependency and more

Hey,
     I was taking a look at my repos and saw that I never sent a PR for that. I fixed the oauth request and cherry picked (if I remember well) commits from other forks too.

Are you interested in those? There is no test for the oauth fix. If you are interested in this PR I guess I could write some tests in a few weeks. Just wanted to see if you are still interested in maintaining this gem or not. No worry if you are not! :)

Regards