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
Change OpenType MIME type to `font/opentype`

Browsers usually ignore the font MIME types and sniff the content
but, Chrome, shows a warning if OpenType fonts aren't served with
the `font/opentype` MIME type: http://i.imgur.com/8c5RN8M.png.

References:
 * h5bp/html5-boilerplate#1317
 * http://mimesniff.spec.whatwg.org/#matching-a-font-type-pattern
Merge pull request #60 from alrra/improvements

Change MIME types for OpenType and WOFF