Remove the unused fcntl import.

When I swapped out fcntl for django's cross-platform abstraction, I neglected
to remove the import. Trivial fix.
Use setuptools instead of distutils for extension packaging.

The extension packaging code was using distutils's classes instead of
setuptools's, which prevented more advanced features like MANIFEST.in
rules from being used. A simple import change fixes this.

Reviewed at https://reviews.reviewboard.org/r/5876/
Set a TRACKING_BRANCH for release-0.8.x in .reviewboardrc.
Merge branch 'release-0.8.x'