New 'last' command

More verbosely, the command is 'show me the details of the last build for this job'. Essentially it's just summarising the details from the /jenkins/job/job1/lastBuild/api/json response. The output looks something like this:

job1 | SUCCESS
 - 2014-03-20T13:20:16.311Z [2 hours ago]

(Note that the status will be "BUILDING" if the job is in the process of being built.)

What do you think? In particular I'm not so sure if mapping of the "result" field to colour in cli.js is the best place for it.