Add Gruntfile.js that concats and minifies CSS/JS and replaces in HTML

[mraible]

I wrote up more information on this in a blog post:

http://raibledesigns.com/rd/entry/using_grunt_with_angularjs_for

[petebacondarwin]

@mraible - thanks for this PR but we are trying to keep angular-seed as simple as possible to get people up to speed with AngularJS itself.
Build steps that are not specific to AngularJS adds extra mental overhead starting out with AngularJS.

[sylver]

I disagree.
Maybe not use this PR as is, but Grunt is nearly essential for an AngularJS project, and @mraible blog post and PR are the most comprehensive I've seen so far and save me lots of hours to use and understand Grunt to unleash all the power of an AngularJS project.
You should seriously consider adding these informations in the angular-seed, one way or another. It's very important for a beginner to know, and what a better place than in the angular-seed repository ?

[karneaud]

+1 but Gulp