[travis-ci] explicit jruby 1.7
[travis-ci] explicit jruby 1.7

jhstatewide/jruby-rack,jruby/jruby-rack,jhstatewide/jruby-rack,jruby/jruby-rack,jruby/jruby-rack,jruby/jruby-rack,jhstatewide/jruby-rack,jruby/jruby-rack,jhstatewide/jruby-rack,jruby/jruby-rack