Refactor of codes in node.js

1) Add async method: `binarySearch` and `btreeSearch`.
2) Refactor of tests by putting them into `tests` folder.
3) Create several new tests in details.
4) Remove useless and reformat codes to be clear.
5) Remove useless snapshots, because they can be recreated when you run `npm run test`.

binding/nodejs/tests/utils/asyncFor.js

@@ -0,0 +1,23 @@
+/**
+ * Async For
+ * @param {Array} groupArray 
+ * @param {Function} exeCallBack 
+ * @param {Function} finalCallBack 
+ */
+function asyncFor(groupArray, exeCallBack, finalCallBack) {
+
+    let i = 0;
+
+    function _innerAsyncLoop() {
+        if (i < groupArray.length) {
+            exeCallBack(groupArray[i++], _innerAsyncLoop);
+        }
+        else {
+            finalCallBack();
+        }
+    }
+
+    _innerAsyncLoop();
+}
+
+module.exports = asyncFor;