Log Message:
Update gh to 1.5.0.

Add ability to comment on issues and pull requests

gh issue comment and gh pr comment commands are now available

Add ability to clone gists

gh gist clone is now available

New Features

- pr view: Display top level review comments inline with regular comments
- repo fork: Add ability to specify fork remote name
- pr merge: Add ability to delete local branch for previously merged PRs

Fixes

- auth: Add more descriptive error messaging when aborting due to environment
  variables
- completion: Improve docs for bash, zsh, fish #2636
- version: Output link to correct tagged release #2638
- Update notification avoids incorrect notifications when gh is built from
  source