eliminate seek()s
quick fix for 2.6
test with zipfiles
Fix zipfile handling; remove py ver test

Since we already have a buffered reader there is no reason to further wrap the
compressed file readers in another buffered reader. This frees us to support
streaming with Python 2.6 as well
include test zip file
despite being buffered we aren't allowed to seek()
Merge branch 'fix/buffered' of github.com:ged-lab/screed into fix/buffered