Add early bailout in areSetsEqual()

Although this probably doesn't matter for our use-case, it is more
complete.

Author: lencioni

src/index.js

@@ -54,6 +54,10 @@ function isReactClass(superClass, scope, globalOptions) {
 }
 
 function areSetsEqual(set1, set2) {
+  if (set1 === set2) {
+    return true
+  }
+
   if (set1.size !== set2.size) {
     return false
   }