Simplify charToDigit and toDigits significantly
Add toDigitsRev
Add doubleOddDigits and doubleEveryOther
Rename doubleOddDigits -> doubleOddIndices
Add sumDigits
Refactor doubleOddIndices -> doubleEvenIndices

Whoops - misread the spec; I ruined the Hubble.
Add validate to solve first problem of hw1
Move hw1.hs -> hw1_creditCardValidator.hs

This will allow me to work on the Towers of Hanoi problem in isolation.
Add hw1 Towers of Hanoi solution

I'm still not entirely sure what I did here, other than to follow Ben
Deane's advice of trusting the recursion, writing out the algorithm
almost verbatim. This breaks down a bit like a binary tree - or perhaps
exactly like one - and all the work ends up as single moves from a to b
down at the leaves, though what a and b are at each leaf is variable.
Move hw1 files into hw1/ folder simplify names

hw2 comes with several files, so it's time to organize a bit.
Merge branch 'hw1'