Fixing missing grunt_command declaration

`grunt_command` was missing after the latest pull request (ver 0.0.8), causing builds to fail:

```
grunt-cli not installed, trying to install it through npm
npm is available
npm version: 1.3.25
installing grunt-cli
/usr/local/bin/npm -> /usr/local/lib/node_modules/npm/bin/npm-cli.js
npm@1.4.4 /usr/local/lib/node_modules/npm
/usr/local/bin/grunt -> /usr/local/lib/node_modules/grunt-cli/bin/grunt
grunt-cli@0.1.13 /usr/local/lib/node_modules/grunt-cli
├── resolve@0.3.1
├── nopt@1.0.10 (abbrev@1.0.4)
└── findup-sync@0.1.2 (lodash@1.0.1, glob@3.1.21)
 deploy
-bash: deploy: command not found
```
(The " deploy" command was sent to bash because `grunt_command` was empty)