Image tutorial notebook edit

Make the Image tutorial more friendly to people using the IPython notebook to follow along (avoid use of set_xxx functions, use arguments to imshow instead.)

Also:
- use scipy.ndimage for image resizing in last example (interpolation)
- minor grammar fixes
- add notes about keeping plt commands in one cell so that effects are shown.
I stripped them out because in the IPython notebook, you can't use them from one cell to the next.  Within a cell, they're still just fine.  I'll make a note to that extent.  This was the issue that tripped up someone I was training on MPL usage - he was trying to use the notebook, and wondering why several commands from this tutorial didn't work.