improved error msg on toBeRehectedWithError and all other built-in async matchers

spec/core/matchers/async/toBeResolvedToSpec.js

@@ -93,7 +93,7 @@ describe('#toBeResolvedTo', function() {
     }
 
     expect(f).toThrowError(
-      'Expected toBeResolvedTo to be called on a promise.'
+      `Expected toBeResolvedTo to be called on a promise but was on a ${typeof actual}.`
     );
   });
 });