Mac OS X WebDAV client uses 'Chunked' instead of 'chunked'

Mac OS X WebDAV client uses 'Chunked' instead of 'chunked'

The Mac OS X WebDAV client uploads files using chunked encoding.  The trick is, when files are copied via the Finder, the headers appear as:

Transfer-Encoding: Chunked

At present, waitress only checks for:

Transfer-Encoding: chunked

A little .lower() magic to fix that issue.