ElectronDensityNode and ElectrostaticPotentialNode are basically the same file

[zepumph]

from code review #30

When comparing the two files in intellij, it looks more like a commit diff than different files, there are about 10 or so changes. It seems like this could probably be combined into a "2DSurfaceNode" or something that both of these nodes can use with options. @pixelzoom please comment if you think this refactoring is not worth the effort.

To me it was a bit confusing to see two fully separate files for the same looking node (just different colors). It also isn't parallel to the general use "SurfaceColorKey.js" which creates a key for any of the surfaces.

[pixelzoom]

Yeah, looks like there should be a SurfaceNode based type.

[pixelzoom]

I factored out SurfaceNode, an abstract base type, in the above commit. The subtypes (ElectronDensityNode and ElectrostaticPotentialNode) implement the updateFill method, which is the bit that differs for these 2 surface types.

@zepumph please review.

[zepumph]

Looks great. Closing