Extensible renderers.

[IanSwift]

Using this library, let's say I want to customize the drawing style. To do so, I would simply need to to extend the "renderer" classes, but currently a good number of the methods in those classes are private, making it hard to extend them. Could you switch them over to protected, so that we could do things like turn our points into pictures of cats? Thanks.

[lecho]

Ok, I will look into that, thanks.

[IanSwift]

I have a pull request ready if you'd like. It's pretty straight forward, just went through the renderer package and changed the private methods to protected. Might have grabbed a couple I didn't need, but I don't see any harm in this change.

[lecho]

Ok, that's great, create pull request:)

[IanSwift]

brb