SERVER_NAME changed to HTTP_HOST

SERVER_NAME changed to HTTP_HOST because SERVER_NAME can cause problems
on some misconfigured hosts. HTTP_HOST is usually more reliable with
those servers. (cf.
http://stackoverflow.com/questions/2297403/http-host-vs-server-name).
This should cause less problem on most hosts.
Better encoding handling in title parsing

Thanks to a patch from Le Hollandais Volant.
Merge branch 'master' of git://github.com/sebsauvage/Shaarli