Add 1.9.3 compatibility

As a friend asked, I made this compatible with 1.9.3 (or I supose to make
it). I just dont know if it's a good idea.

By one side, 1.9.3 is a supported ruby version ATM (probably it will be for some
time).

By the other, I really would like to ignore this old version.

To let things more complecated, the company I work hava many 1.9.3
projects.

I really dont know what to do :(

what do you guys think? @leafac