Update Grunt configuration some.

The Grunt configuration for Backbone.Picky is a bit out of date. This 
attempts to update it in a minimal, just-make-it-work way.

* `grunt.js` renamed to `Gruntfile.js`
* Update project version in `package.json`
* Add jshint and uglify dependencies as they are no longer bundled 
  directly into Grunt
* Use `package.json` version in Gruntfile banner text
* Update rigger, uglify and jshint configurations
* Use new `grunt.registerTask` interface