Initial implementation of the adventure xblock

Initial implementation of the adventure xblock, build with Backbone + Marionette.

It currently only read the raw xml config.... but this will be modified to use lightchildren. To make this testable on the client side, we can only mock the function that fetch the data in the controller.
I think the code here should reflect more clearly why the ooyala children need special-case treatment. Event better would be to eliminate the special-case treatment altogether. Would it be possible to do something like this instead?
```
    @property
    def complex_children(self):
        """
        These child blocks need to be loaded with jquery-xblock because they
        need JS/CSS/etc. and cannot be rendered as static HTML only.
        e.g. ooyala video blocks
        """

        players = ([(child.name, child) for child in self.get_children_objects()
                    if child.requires_javascript_or_css])

        return players
```