Improve inline comments about `AddEncoding`
Improve inline comments about `AddEncoding`

Explain better what the `AddEncoding` directive does as it seems that
people are confused by its usage (see: https://github.com/h5bp/server-configs-apache/issues/16#issuecomment-52095603).

Ref: http://httpd.apache.org/docs/current/mod/mod_mime.html#addencoding

atyenoria/server-configs-apache,blackmoral/server-configs-apache,voku/server-configs-apache,StephanieMak/server-configs-apache,sengkoil/server-configs-apache,atyenoria/server-configs-apache,Gillespie59/server-configs-apache,Gillespie59/server-configs-apache,walterebert/server-configs-apache,sengkoil/server-configs-apache,johnnyicarus/server-configs-apache,voku/server-configs-apache,StephanieMak/server-configs-apache,johnnyicarus/server-configs-apache,blackmoral/server-configs-apache,h5bp/server-configs-apache,walterebert/server-configs-apache