Adding s_srs and t_srs flag support

Hi Wavded,
after asking you to modify the code, i've forked the project and run it locally. I've successfully make it run with the new 2 flag for submit correct projection and maybe you want to integrate this feature. I've never use nodejs but i've already written a little in javascript. Maybe you can improve my code 'cause is poorly written! My bad.. but it works ;) I'm at work now so i can't spend so much time on it. Maybe tomorrow i'll  perfect it.. Sorry for my bad English!

Bye,
Daniele