py3 changes for outfilter.py

I started running this with dib where we have pure python3
environments and it failed.

You can't have unbuffered text i/o in python3 for ... reasons? [1]
Changing the file to binary mode works around this.  Python3 opens
sys.stdin in text mode, so we need to manually convert the unicode
strings to bytes before we write them to the binary file.

[1] http://bugs.python.org/issue17404

Change-Id: Iebb26f0d3c2347d262cbc10dfd0912840cd05878
1 file changed