Add a note about more use cases for template false

Fixes #1655
Hmmm...I don't think of 'attaching' my view to anything, really. I find it more familiar if it said something like:

> Another use case is for when your View's element is dynamically generated, such as in the case of an SVG or canvas element. In those cases, you can give the view a `tagName` and then create the DOM manually in the `onRender` callback.