Updated Ruby version from 2.1.0 to 2.1.1

Change-Id: I57c4b7bce4b139c39c00f4619aa35d8559497c05
Added parallel_tests as runtime dependency

Change-Id: Ib4073655c97b480906165653f122b045d0bdbe70
Merge branch 'master' of https://gerrit.wikimedia.org/r/mediawiki/selenium