refactor(config.js): Extract config file

* Separate different config source to each files
* Freeze config object

lib/config/enum.js

@@ -0,0 +1,16 @@
+'use strict'
+
+exports.Environment = {
+  development: 'development',
+  production: 'production',
+  test: 'test'
+}
+
+exports.Permission = {
+  freely: 'freely',
+  editable: 'editable',
+  limited: 'limited',
+  locked: 'locked',
+  protected: 'protected',
+  private: 'private'
+}