Revert "Using RegExp replace loop in isHidden (#109)" (#138)

This reverts commit 8330028.

index.js

@@ -147,10 +147,11 @@ async function send (ctx, path, opts = {}) {
  */
 
 function isHidden (root, path) {
-  const hiddenFileReg = new RegExp(`${sep}\\.`)
-  path = path.substr(root.length)
-
-  return hiddenFileReg.test(path)
+  path = path.substr(root.length).split(sep)
+  for (let i = 0; i < path.length; i++) {
+    if (path[i][0] === '.') return true
+  }
+  return false
 }
 
 /**