Implement initial version of aks utility with isAKSWitness

Also add .gitignore file.
Implement getFirstAKSWitness in aks utility
Implement and use concurrent witness-finding
Make aks utility take command-line input
Add naive trial division algorithm in arith.go
Factor out factorOut function in TrialDivide

Also improve testTrialDivide test output a bit.
Break in TrialDivide when d > t
Use a mod-30 wheel in TrialDivide
Implement CalculateEulerPhiPrimePower()
Implement FloorRoot()
Use FloorRoot() in TrialDivide()
Implement CalculateMultiplicativeOrderPrimePower()
Implement CalculateMultiplicativeOrder()
Implement calculation of AKS modulus

Also implement Min() and Max() for big.Int.
Implement simple calculation of AKS upper bound
Implement CalculateEulerPhi()

Use it in calculateAKSUpperBound().
Keep track of an upper bound in TrialDivide
Add upperBound parameter to TrialDivide
Trial-divide up to M
Add benchmarks for isAKSWitness