Move python sourcing script to plugin file

Undoes most of https://github.com/bbchung/clighter/commit/6f45a33d7b18121722a2ec060369adc7b7b5d04b based on my comment https://github.com/bbchung/clighter/pull/3#issuecomment-48993289

I cannot get this to work unless it is in the plugin file. When the python functions are called other places in the autoload file they throw an error because they are undefined. If I'm missing something about how this works please let me know!