mod_http_files: send valid ETag header
RFC 2616 section 14 (header field definitions) shows that ETag header content
should be wrapped in double quotes.
For full information on our dependencies, version requirements, and
where to find them, see http://prosody.im/doc/depends
If you have luarocks available on your platform, install the following:
- luaexpat
- luasocket
- luafilesystem
- luasec