Edited Plots from Chapter0

My purpose was to make the plots closer in appearance to the original plots in the book, by formatting the axes and the legends. Another important purpose was to generate standalone pdf/png files of the plots for insertion into presentations. 

The original png files were of low quality, perhaps it was intended to keep file size down, not sure, but I attempted to raise the quality. This is a first commit as I'm just learning to use github and github for mac, so it's more of an experiment. I intend to modify more of the graphs in the future as the need arises.