docs(pkg): update help URL to https://deis.com/

[mboersma]

Summary of Changes

Updates the URL printed after a successful git push to https://deis.com/ instead of http://docs.deis.io/.

Issue(s) that this PR References

See deis/example-clojure-ring#5.

Testing Instructions

The output of a successful git push for an app should reference the above URL, not anything at deis.io.

Pull Request Hygiene TODOs

Please make sure the below checklist is complete.

• [X] Your pull request is concise and to the point (make another PR for refactoring nearby code)
• [X] Your commits follow the commit style guidelines

[bacongobbler]

this would probably be a good change to get into v2.0. yay or nay?

[bacongobbler]

@sgoings thinks this should go into 2.0. Marking as such!