Pinyinconverter small improvement

Hello! I'm a chinese born in Spain, and in my spare time I teach chinese to some people.
For a exercise for my students I searched for a way to type pinyin easily and stumbled upon your blog, and saw your jquery plugin, it's fantastic, simple and just does what you expect.

My inner amateur developer felt the need to improve the user experience a bit, so I changed it so when you 'keyup' on the keys 1 to 4 it updates the translation directly into the input, instead of having to press the button. You can see the result realtime on http://aleation.com/pinyin If you like accept the pull request, I also updated the minified js, the only thing I didn't change is the explanation on the index.php because I don't know if you might accept the pull request.

And I'm completely new to github, this is my first Fork/contribution or whathever so sorry in advance if I messed up with anything