Request: new slack integration command

[shiboe]

Would be nice to have a new command that lists the last deploy(s) for an environment. Default could show the most recent, then it could accept a parameter to show that many.

example:

Stephen Cave
/deepthought show staging

Deep Thought
Last deploy to staging was develop-branch at 12:55pm PST on 4/12/1945

Stephen Cave
/deepthought show staging last 3

Deep Thought
The last 3 deploys to staging were:
- develop-branch at 12:55pm PST on 4/12/1945
- fancy-hat-branch at 9:09am PST on 4/11/1945
- develop-branch at 5:00pm PST on 9/30/1944