Use assemble.io for Handlebars templates

This is just a *VERY* basic assemble setup which might require
further tweaking in the future, but it's a nice starting point to
use Handlebars templates for static HTML.
This will work better with assemble
Fix modernizr task

modernizr needs to be a multitask and files needs to be an object
here. See http://goo.gl/7GpT1g and below for details.
Use more explicit target
Update docs to reflect changes
Update grunt plugins to recent versions
Update JS plugins to recent versions
Bump version number