Make changes to have wechat-rails running in Ruby 1.9

1. Get rid of keyword arguments;
2. Use Array.include? to test if an element is in an array.

Some trailing white spaces are also cleaned up in this commit.
Hm with your changes, I think you'd still be able to call this like `item(title: "My Article", description: "My description")` right? So it is kind of compatible =P