Modularized CoffeeScript-based Backbone refactor

This pull request is a complete refactor and modularization of BackboneJS for CoffeeScript, using Grunt for task automation.  As of this request, all files are building successfully and existing tests are passing.  The only Grunt task in need of development docco compilation (all others have been rebuilt in Grunt from the existing Rakefile).  No functional code changes have been made.  See Travis build:  https://travis-ci.org/distilldesign/backbone

It's far easier to think of Backbone as a series of modules (Events, Model, Collection, View, etc).  And maintaining modules, with automatic build automation, is far easier and safer.

Using CoffeeScript we can separate out modules into individual CoffeeScript files.  Checkout the coffee sources in coffee/.  Easier maintenance!  

Using Grunt, we can automate builds for backbone.js and -min.js from CoffeeScript sources.  And we can execute qunit tests.  Checkout Gruntfile.coffee.

I hope you'll consider granting this pull request as a way to modernize Backbone development going forward.