Try to use in-jvm reuse to speed up spawning

7 jobs for master in 15 minutes and 59 seconds
Status Job ID Name Coverage
  Syntax
passed #525
ruby
jruby_1.7

00:11:31

passed #526
ruby
jruby_9.1

00:14:22

passed #521
ruby
ruby_2.1

00:00:42

passed #522
ruby
ruby_2.2

00:00:52

passed #523
ruby
ruby_2.3

00:01:08

passed #524
ruby
ruby_2.4

00:00:35

 
  Linting
passed #527
ruby
rubocop

00:00:54