Plot hidden units, make a basic test function.

@vishaalprasad - after making these changes, I have a question on Test 2 and 3.  On many of my runs, most units fail to connect to the hidden unit location.  This is the most probable location to connect to, so it's a little odd.

Probably it's just a sampling thing, but could you take a look at the plots and make sure you think it's reasonable that the hidden unit location is connected so infrequently?  Perhaps we should make a test case with a small $\sigma$ and large number of connections...