Initial pass on python 3 port

Given the imminent end-of-life for Python 2, I didn't bother making the
codebase compatible with both.

Signed-off-by: Drew DeVault <sir@cmpwn.com>

whipper/command/offset.py

@@ -177,7 +177,7 @@ CD in the AccurateRip database."""
         logger.debug('ripping track %r with offset %d...', track, offset)
 
         fd, path = tempfile.mkstemp(
-            suffix=u'.track%02d.offset%d.whipper.wav' % (
+            suffix='.track%02d.offset%d.whipper.wav' % (
                 track, offset))
         os.close(fd)