1.1.0 beta amd support

I have add module/AMD support to both ```Backbone.Modal``` and ```Backbone.Marionette.Modals```.

I surrounded the classes with:
```coffee
do (root = @, factory = (Backbone) ->
  # class Backbone.Modal extends Backbone.View
  # ...
) ->
  if typeof exports is 'object'
    backbone = require 'backbone'
    module.exports = factory backbone
  else if typeof define is 'function' && define.amd
    define ['backbone'], factory
  else
    unless Backbone?
      throw new Error("Backbone is not defined. Please include the latest version from http://documentcloud.github.com/backbone/backbone.js")

    factory Backbone
```