Separate main.js into some modules.

Helper functions and the plugin function are separated.

src/js/lib/helper.js

@@ -0,0 +1,36 @@
+/* Copyright (c) 2015 Hyunje Alex Jun and other contributors
+ * Licensed under the MIT License
+ */
+'use strict';
+
+exports.toInt = function (x) {
+  if (typeof x === 'string') {
+    return parseInt(x, 10);
+  } else {
+    return ~~x;
+  }
+};
+
+exports.isWebKit = 'WebkitAppearance' in document.documentElement.style;
+
+exports.clone = function (obj) {
+  if (obj === null) {
+    return null;
+  } else if (typeof obj === 'object') {
+    var result = {};
+    for (var key in obj) {
+      result[key] = this.clone(obj[key]);
+    }
+    return result;
+  } else {
+    return obj;
+  }
+};
+
+exports.extend = function (original, source) {
+  var result = this.clone(original);
+  for (var key in source) {
+    result = this.clone(source[key]);
+  }
+  return result;
+};