MFH: r386626

devel/ruby-gems: update to 2.4.7

PR: 200264
Differential Revision: https://reviews.freebsd.org/D2572
Submitted by: Santiago Pastorino <spastorino@gmail.com>
Approved by: mat (mentor)
Security: CVE-2015-3900

Approved by: ports-secteam (delphij)