Don't depend on php-xsl which is a virtual package, nowadays depending
on php-xml is the right thing to do.
This also fixes a warning from cme:
Warning in 'control binary:tweeper Depends:3' value 'php-xsl': \
package php-xsl is unknown. Check for typos if not a virtual package.
Package: tweeper
Architecture: all
-Depends: ${misc:Depends}, php-cli, php-curl, php-xsl, php-symfony-serializer,
+Depends: ${misc:Depends}, php-cli, php-curl, php-xml, php-symfony-serializer,
php-symfony-property-access
Suggests: libapache2-mod-php | php-cgi
Description: web scraper to convert supported websites (e.g. Twitter.com) to RSS