"Error:" doesn't display correctly falsy "actual" or "expected" values.

[cowboy]

Right now when an assertion like this fails:

test.ok(undefined, 'this value should be truthy');

We see this:

>> my test
>> Message: this value should be truthy
>> Error: this value should be truthy

But we should really see this:

>> my test
>> Message: this value should be truthy
>> Error: undefined == true

I think the fix is to change this line inside betterErrors:

if (!e || !e.actual || !e.expected) { return assertion; }

To this:

if (!e || !('actual' in e) || !('expected' in e)) { return assertion; }