Create example of configuring a marker's anchor

The ability to configure a marker's anchor point using Google Maps is
less than intuitive. Although the documentation makes it sound like you
can configure it via a MarkerOptions object, that doesn't seem to work
with this library.  As such, you need to configure the anchor point on
the image itself.  This example demonstrates how to do that.
Merge pull request #677 from mminella/markerAnchorExample

Create example of configuring a marker's anchor