Namespace fixes in readme

Not sure if there are other problems too. This change will make getting started a little smoother for folks.

Note that without requiring `[clojure.test.check.clojure-test]`

You get 

    WARNING: Use of undeclared Var clojure.test.check.clojure-test/*default-test-count*

Maybe clojure.test.check should require that file?