Prime number tester(s)

Prime numbers are a common occurrence in Project Euler problems, and as such we require a fast, efficient method for determining whether a given number is or is not prime.

One popular algorithm, adopted by PyPE, is the Miller–Rabin primality test (http://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_primality_test). This is a probabilistic algorithm that is commonly used in large-number mathematics and is fairly reliable.