Euclidian Algorithms

[samjones246]

Implementations of both the Euclidian Algorithm and the Extended Euclidian Algorithm. The first computes the greatest common divisor of two integers. The second computes the coefficients of Bézout's identity for given values of a and b, but the version I have implemented uses this to find the multiplicative inverse of a modulo b. This is a common use for the algorithm in cryptography.