Added support for the ``expand`` option for Issues

The ```expand``` option is used to specify resource expansion in the
Jira REST API.

It's particularly useful for things like fetching the ```changelog``` of
an Issue.

This PR adds the support to the ```ListIssues``` and ```ViewIssue```
functions of the ```jira.Cli``` struct.

I'm happy to add tests, but there is currently no test suite in the
master branch, so I did not want to bog down the PR with tangential features.

main/main.go

@@ -203,6 +203,7 @@ Command Options:
 		"remove":                setopt,
 		"r|reporter=s":          setopt,
 		"f|queryfields=s":       setopt,
+		"x|expand=s":            setopt,
 		"s|sort=s":              setopt,
 		"l|limit|max_results=i": setopt,
 		"o|override=s%":         &opts,