add OAuth2 drop-in for Disqus

- changed BaseAuth.urlopen_access_token to take an optional
  api_key parameter
- also includes little tweaks that flycheck complained about
  in other modules
add disqus configs to .gitignore
disqus: add a default scope and access_denied handling
Merge pull request #6 from kylewm/master

add OAuth2 drop-in for Disqus