Description of problem:
When clicking 'po' download link, content type of the transmitted file is application/octet-stream, but text/plain would be more appropriate for the po format.
Version-Release number of selected component (if applicable):
Changed po and pot download links to use text/plain in 2.1-SNAPSHOT. Raw formats still transfer using application/octet-stream.
VERIFIED with Zanata version 2.1-SNAPSHOT (20121206-1113)