Deal with chaco.example_support

The file https://github.com/enthought/chaco/blob/master/chaco/example_support.py exists, but is unuseed in the codebase. Instead, we use a similar `example_support` module living in enable (which we probably shouldn't be doing!).

We should either update chaco examples to use this module instead of using enable, or this module should be deleted. If the module does stay in chaco, it should be moved to sit in `chaco/examples`.