Added new test; little bit of refactoring.

Changed the word "sigma" to "variance" to better indicate the reasoning.
Added in a new test ("ratio test"), including helper function in there.
Added a function variable in main to cleanly switch from one test to another.
Added an if conditional on the fourth test to make sure it's not the "ratio test" which runs too slowly.
Removed print statement in createConnectionMatrix.
I agree that `sigma` is not a great parameter name (though somewhat standard).  However, `sigma` is actually the standard deviation, which is the square root of the variance.  So, `sigma` or some form of `standard deviation` seem better to me.