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 think so! That said, I've never used Ruby 2.0, so I'd want to double check :)  Of course you can worry about merging back upstream when the time comes, I guess there is no hurry.