Compatibility with ST2 and ST3

Hi,

I just noticed that you were working on ST3 compatibility. 
I've done the same in the meanwhile, and also made sure that it's backward compatible with Python 2.6 (ST2).
Also made sure that UTF8 conversions still work as expected :) In ST3 they had stopped working, one of the reasons being that json.dumps returns a str, which doesn't have a .decode() method anymore, so to preserve UTF8 codepoints, I used the  ensure_ascii=False parameter of dumps instead.