pass view instance in calls to Marionette.Renderer.render

Enable custom `Marionette.Renderer` implementations access to the view instance in which `render` was called.  This is useful in such scenarios as defining Mustache partials for a view, or even defining per-view templating engines.

Replaces calls:

    Marionette.Renderer.render(template, data)

with:

    Marionette.Renderer.render(template, data, this)

*this* being the view instance.