subplot(x, x, 0) should raise Exception

[twiecki]

I'm sure I'm not the only one who used this idiom:

for i in range(4):
   plt.subplot(2, 2, i)

And got confused that the subplots show up in the wrong order. Understandbly, subplot uses 1-based indexing. But what about throwing an exception if 0 is passed, that would save a lot of wasted hours tracking down this odd behavior.

[tacaswell]

As a clarification, the odd thing here is that 0 shows up last.