fix for issue #212; avoid sending code in communicate()

I managed to reproduce the crash from #212 in a separate program: https://gist.github.com/3885571

Warning: I'm not a pythonist, and I have no idea why the code didn't work in the first place (and it's fixed in Python 2.7). But the fix is straightforward and it works.

To find the issue, I commented out all of the SublimeLinter code and progressively uncommented parts of it until the crash appeared.