Merge commit #235 gonum/plot#235

Documentation is available at:

https://godoc.org/github.com/gonum/plot

You can get gonum/plot using go get:

go get github.com/mison201/plot/...

If you write a cool plotter that you think others may be interested in using, please post to the list so that we can link to it in the gonum/plot wiki or possibly integrate it into the plotter package.