Add command for installing/updating libraries

[recidive]

We need to add a script or command to choko script for installing all npm and bower dependecies for an application.

This could make use of Grunt.

Depends on #135.

[lucasconstantino]

About the usage of Grunt, the ommunity is moving fast to the usage of Gulp. Particularly I've never had the chance to use Gulp, but I think we should give it a try.