Add support for `-o/--browse` option for pull-request
Support `protocol` option in config file

Defaults to HTTPS, but can be used to configure Enterprise instances
which are only accessible over HTTP.
Find host instead of prompt host when creating project
Support verbose mode via HUB_VERBOSE environment variable

This dumps information about HTTP traffic on stderr
Use repo name from response when merging pull request
Exit with error if command-line flag parsing fails