Adding unit tests

1. There have been several minor optimization been done in this week, like the primes of the factor_base which make a have been given a bound of [1000, 5000]. The lower bound ensures that there are very less redundant relations (<~1%) and the upper bound ensures that with a single a we are able to make many polynomials for sieving.

2. Another major part of this week works was to implement unit tests for every functions.

3. I also performed performance comparision of QS with ECM. QS was ale to factorize a 50 digit number within ~8 mins while ECM took longer than QS to do the same factorization.