ENMTools R package model plots are now all done in ggplot2

Newest update (I did say they'd be coming very rapidly now, didn't I?): I've switched the enmtools model plots from using base raster plotting functions to using ggplot2.  They don't actually look very different, as you can see by comparing base (top) to ggplot2 (bottom) plots:

However the switch to ggplot2 allows for a lot more flexibility down the line, and also makes it easier to store plots as objects for future manipulation.