Adds a freq function

freq takes a list of integers and returns a list of the number of occurences of the digits 0-9. Note, I've changed all Int data types in freq and count to Integer to appease the compiler.
Adds asterisk function

asterisk builds each vertical line of the histogram
Adds pad function

Ensures all lines are right padded with spaces so that all line lengths 10.
Adds rotNeg90 function

rotNeg90 returns the lines of the histogram rotated 90º counterclockwise so they may be output in the desired format.
Adds squeeze function

squeeze takes a list of histogram lines and removes any that are 10 blank spaces.
Adds histogram function

Finally, putting all the pieces together, histogram returns the actual string output of the chart. Thrilled it works, but don't think I'll be an expert Haskell code golfer for quite some time.