More cleanup.
- readMatrix now works for 13.
- Cleanup redundancy by using listArray in 23.
- Replace hand-rolled modPow w/ library.
Smarter cleanup of 26 thru 29.
- Reduce search space to primes on 26.
- Also use mult. order instead of list searches on 26.
- Reduce search space on 27 too, use maximumBy to defer calculations.
- Improve speed on 29 by using ordered union rather than naive nub.
Cleanup 30 - 39.
- Speed up 34 by memoizing factorial calculations.
- Speed up 36 by only checking base-10 palindromes.
- 39 might as well use intSqrt.