Advent of Code 2015

Codes from Christmas coding event.

Useful functionalities:

String.prototype.isNumber (is string a number?) - day 7
getAllPermutations (gets all permutations of an array) - day 9
md5 - (counts md5 hash) - day 4
sumDivisors (two versions), logDivisors - (for counting divisors of a number) - day 20