Fix for Mac OSX (and others?)

Twee doesn't work on Mac OSX in the Terminal. With this modification, it will.

WARNING: I only tested in Mac OSX 10.7. It could very well break stuff on other platforms.

I've found the fix there: https://groups.google.com/d/msg/tweecode/ik1ppjTomGY/5Xc0g-LeRVMJ