The noplot argument in plot.sph.image() did nothing.  I've fixed this.
Revert "The noplot argument in plot.sph.image() did nothing.  I've fixed this."

This reverts commit e315db8df1d08f6302c55131d46ee849e352a57a.
The noplot argument in plot.sph.image makes image() return the numpy
array of the image, and does not call any code from pyplot, as apontzen
recommended in the comments of #122.
Merge pull request #123 from bwkeller/master

Fixed noplot argument in plot.sph.image()