Pull cukes from master into gh branch

The Ruby version of hub from master branch has had tweaks since the "gh" branch was started, so this merges in the master branch to get the cukes changes. Naturally, this introduces some new failures since the Go version needs to be updated. I'll try to fix some of the failures myself over the weekend.

The features in master were:

- e723fd3
- 6558a9f
- c54a789 - Enable API debug output by setting HUB_VERBOSE
- 1e4477b - Fix reusing old OAuth tokens stored in Authorizations API
- 0f44f3e - Respect `note_url`, not `app.url` field in Authorizations API
- ea74102 - Add option to open pull request in browser.
- 641ea1d - Make `browse` and `compare` respect `protocol` config option
- 7944d63 - Support Enterprise over HTTP via `protocol` config option

The tricky features to add will be support for HUB_VERBOSE environment variable for debugging, and supporting `protocol` config option in the new TOML file.

/cc @jingweno