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.
Please leave the  `set_cmap` in at least one of the cases.