Add plot methods for circular, elliptical, and rectanglular apertures
Add plot() abstractmethod
Use matplotlib.patches for Circle
Add initial plot methods for CircularAnnulus and EllipticalAnnulus
Updated plot methods for CircularAnnulus and EllipticalAnnulus
Update make_gaussian_image example
Merge pull request #113 from larrybradley/plot_apertures

Add plot() method to the aperture classes