Fix example to follow latest analysis API

[astrofrog]

Since the analysis properties are now quantities, we need to take their values. This makes me think that it might be nice to have it that one can transform a structure to a patch (ellipse) easily, e.g. PPStatistic.to_mpl_ellipse or something similar. @ChrisBeaumont - what do you think?

[astrofrog]

Actually I'm curious why Matplotlib doesn't accept the quantities as they are. I also need to make sure that all the analysis code is compatible with Astropy 0.2.

[ChrisBeaumont]

+1 on to_mpl_ellipse -- the code is ugly enough to hide behind a method

[astrofrog]

Ok, will work on that!

[astrofrog]

@ChrisBeaumont - I've now implemented to_mpl_ellipse - does this seem ok to you?

[ChrisBeaumont]

This looks good.

Can you explain the benefit of the abc module? Is it just that it catches unimplemented methods earlier?

[astrofrog]

@ChrisBeaumont - yes, the issue is that I didn't want to repeat the to_mpl_ellipse method, but it relies on things that only get implemented in sub-classes, it's a way to make sure (a) that you can't use the base class directly, and (b) that the methods get implemented in sub-classes.

[ChrisBeaumont]

Thanks. This looks good to me