Add deploy commands for dashboard

[cohitre]

I would like to have wubot deploy dashboard 1.2.1 live and wubot deploy dashboard 1.3.0 preview commands.

To deploy the dashboard to dashboard.balancedpayments.com we do the following

1. have a copy of the dashboard project
2. run npm install to make sure all dependencies are up to date
3. run grunt deploy

To deploy the dashboard to dp.balancedpayments.com we do the following

1. have a copy of the dashboard project
2. update the package.json to include "balanced-admin": "balanced/balanced-admin" as a dependency. As long as wubot has access to that repo it should be able to install balanced-admin using step 3.
3. run npm install to make sure all dependencies are up to date
4. run grunt deployPreview

[mjallday]

we should take this chance to make it deploy a specific tag so it's easy to roll back to a previous version

[cohitre]

We already tag dashboard builds and use those for deploying, I check them out locally using git co vX.Y.Z and then deploy. It'd be sweet if hubot could handle that.