Always generate consistent gzip
Change WOFF MIME type to `application/font-woff`

The WOFF MIME Type was formally registered as `application/font-woff`:
- http://www.iana.org/assignments/media-types/application/font-woff
Merge pull request #591 from alrra/woff-mime-type

Change WOFF MIME type to `application/font-woff`