Merge branch 'Volox-ie11-sets-support'

- Merges #1478 from @Volox
- Fixes #1355

spec/helpers/checkForSet.js

@@ -3,9 +3,29 @@
     if (typeof Set === 'undefined') { return false; }
 
     try {
-      var s = new Set([4]);
-      if (s.size !== 1) { return false; }
-      if (s.values().next().value !== 4) { return false; }
+      var s = new Set();
+      s.add(1);
+      s.add(2);
+
+      if (s.size !== 2) { return false; }
+      if (s.has(1) !== true) { return false; }
+
+      var iterations = 0;
+      var isForEachWorking = true;
+      s.forEach(function(value, key, set) {
+        isForEachWorking = isForEachWorking && set === s;
+
+        if (iterations===0) {
+          isForEachWorking = isForEachWorking && (key===value) && value===1;
+        } else if (iterations===1) {
+          isForEachWorking = isForEachWorking && (key===value) && value===2;
+        }
+
+        iterations++;
+      });
+      if (iterations !== 2) { return false; }
+      if (isForEachWorking !== true) { return false; }
+
       return true;
     } catch(e) {
       return false;