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.
Just stumbled across this, and a small question: is there a reason you use (and thus recommend) `--matplotlib` intead of the cell magic `%matplotlib`. I personally think using the flag is always a bad habit, as using `%matplotlib` makes sure someone else can run your notebook as is (and does not need to start the notebook kernel in a specific way)