Needs random tests

This duplicates the "Function Cache" kata: http://www.codewars.com/kata/525481903700c1a1ff0000e1/. The exact same solution works for both.

Everything looks good, could be improved by adding a few test cases

User test cases

Nearly identical to an existing kata: http://www.codewars.com/kata/525481903700c1a1ff0000e1

Should add some tests for "Run tests", and details for fail tests.

Default test cases please.

If the reference returned by report() is supposed to match the current values, not a snapshot, then the description needs to say this. Ideally with an example, e.g.

var spied = spy(fn), report = spied.report();
report.totalCalls === 0; // spied has not been called yet
spied(1);
report.totalCalls === 1; // spied has been called once
spied("a");
report.totalCalls === 2; // spied has been called twice

Need to create a test case that evaluates different functions don't share the same cache.

function hello(){return 'hello';}
function world(){return 'world';}
var cachedHello = memoize(hello),
cachedWorld = memoize(world);

Test.assert(cachedHello(1) != cachedWorld(1));