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.
I agree with @jasonkb that if we want to fix the style, we should fix them all. 

And as we can't use the keyword arguments, it's probably impossible to maintain compatibility with the original upstream. If that's the case, we probably will never be able to merge our changes to upstream.