Add docs, iteration param and bug fix

[adamilardi]

K should be K-1 since that will be last last element of the array. It only noticed it go wrong when you pass in bad input like [0]
I added iterations to test out some of the -H param values

[adamilardi]

If you run this command on the new code you'll see this error
python findDirichletPrior.py -H1,4,5 < /dev/null -i 500000

dirichletMultinomialEstimation.py", line 101, in getPredictedStep
b = numSum / ((1.0/hConst) + denSum)
ZeroDivisionError: float division by zero

[maxsklar]

My original intent was to make "K" the error value. But that's kind of counter-intuitive, so I'll keep it like this.

[adamilardi]

You can always chuck in some asserts if you still want to error
assert(sum(distribution) > 0)