use dep tool to manage dependencies & add the ability to kill -9 cmd

[dovreshef]

No description provided.

[coveralls]

Coverage decreased (-1.7%) to 98.256% when pulling 0122c77 on dovreshef:master into a2f1810 on go-cmd:master.

[daniel-nichter]

Let's do this in separate PRs: dep and Stop timeout. dep doesn't impact usage, but the Stop timeout changes/breaks the current API, and we shouldn't do that to current users. I have another PR open for streaming output that would allow a Stop timeout via another mechanism that won't break the API. I like the idea of Stop(timeout time.Duration), but I'll need to tag the current API 1.0.0 and make that backward-incompatible change in 1.1.0.

[daniel-nichter]

And I just noticed the original timestamp on this PR. It's been quite awhile. Sorry :-) If you can still work on this, great! If not, we can close this and I can make the changes.

[dovreshef]

Sorry. I have moved away from the project using this. Closing..
Thanks for creating this!!