Documented some common questions about QuickCheck

· Generating arbitrary instances for bespoke
data types (http://stackoverflow.com/questions/16440208/how-to-generate-arbitrary-instances-of-a-simple-type-for-quickcheck)
· Increasing number of tests (http://stackoverflow.com/questions/8116262/how-to-get-haskell-quickcheck-2-4-to-increase-tests)