www/piwik: update 2.8.0 -> 2.8.3

PR:		194520
Submitted by:	Hans Fredrik Nordhaug <hans@nordhaug.priv.no>
Approved by:	mentors (implicit)


git-svn-id: svn+ssh://svn.freebsd.org/ports/head@372141 35697150-7ecd-e111-bb59-0022644237b5