- non-existent file simply returns an error
- corrupt file (e.g. YAML unmarshal error) also returns an error
- if there were errors, just check for new release normally instead of aborting
- Only report an update available if the version number of the release
is greater than the current version
- Removes `command` dependency from `update` package; instead, pass
current version as an argument
- Remove `brew upgrade` instructions since we can't be certain that gh
was installed via Homebrew in the first place.
- Does not check for updates unless stderr is a tty
- Preserve stderr color output even if stdout is not a tty
- Fixes stderr color output on Windows
