"heroku addons:add mongohq", add is deprecated

[fcagalj]

It should be used "heroku addons:create mongohq" instead.

I also suggest using MongoLab as default DB because it offer free plan. MongoHQ doesnt offer free plan any more...

[Awk34]

I can't find where we reference the deprecated command. In the README, the command that we reference is heroku addons:create mongolab.

[fcagalj]

It is inside heroku/index.js generator. It is not task but instructions to use add:mongohq instead of create:mongolab. I created PR.

#1226

[Awk34]

Aha! I was just looking in the doc files, not it the JS. Thanks for the PR!

[kingcody]

Closed by #1226