Paypal charset

PayPal notifications come with a charset parameter indicating which charset they're in. This patch will look at that charset and then convert the parameter values to UTF-8 so that you can safely read the strings that come in.

I guess this won't work with Ruby 1.8, and I also guess another solution would be to not re-encode but to just set the encoding on the strings so you're free to do what you want with it later.