Factorization algorithm

The algorithm for factoring a number n as I've implemented it goes something like the following.

• Trial division. Using a precomputed number of primes (currently all those less than 1 million), test if any divide n. If so, add them as factors, divide n by them, and continue

• Perfect power test. Details here: https://github.com/dkhofer/primes/wiki/Finding-perfect-powers

• Pollard's Rho algorithm.

• Brute force