Eliminate implementation-specific tests

Inspired by a review of #149 (fix for #148) - a new test was failing based on a (IMHO) poorly constructed state atom in the robot-names exercise example; one of the beauties of Clojure, and, _a fortiori,_ testing in Clojure is being able to test pure functions with pure functions, rather than relying on underlying implementation details for mutable state.

This issue calls for a review of all tests in @exercism/clojure and there related examples to ensure that tests only check for functionality without relying on the behavior of particular stateful constructs to pass.