Upgrade Miller-Rabin primality test to improve accuracy.

[tfdahlin]

Certain composite integers have a very large quantity of non-witnesses, which means more tests are required to confirm they are indeed composite. If we can more quickly identify these numbers, it means our primality tests for certain composite numbers will end more quickly, effectively speeding up our primality testing in general. Implementation of this might be non-trivial though, as I haven't finished reading the paper yet.

Reference: Improving the Speed and Accuracy of the Miller-Rabin Primality Test

[tfdahlin]

I might also look at implementing Baillie-PSW primality testing instead, but I can't seem to find anything that compares the two.