update for v 2.0.0

util/index.js

@@ -0,0 +1,7 @@
+export function randomExtend (minNum, maxNum) {
+  if (arguments.length === 1) {
+    return parseInt(Math.random() * minNum + 1, 10)
+  } else {
+    return parseInt(Math.random() * (maxNum - minNum + 1) + minNum, 10)
+  }
+}