Added function to calculate nCr
Solved Project Euler problem #15
Added digit_sum function to library.
Solved Project Euler problem #16
Added magnitude function to library.
Solved Project Euler problem #17
Solved Project Euler problem #18
Changed helper to allow a flag for stubbing get_input()
Updated minor syntax error.
Solved Project Euler problem #67
Solved Project Euler problem #22
Solved Project Euler problem #20... Felt like cheating in Python.
Fixed minor formatting issue.
Solved Project Euler problem #11
Added function to compute the proper divisors of a number.
Minor comment changes.
Added flag for prime_factor() to allow for factors in a list or dictionary. Updated some comments.
Added helper function to generate primes to a certain number.
Added generator for abundant or deficient numbers.
Changed abundant generating function. Fixed bug in prime and divisor generators.