Run latest precompiled JRuby on CI only against ActionPack

Uses latest precompiled JRuby so that
we don't spend time downloading versions Travis has
not already compiled. http://rubies.travis-ci.org/

Uses latest jdk: oraclejdk8
per
https://docs.travis-ci.com/user/build-environment-updates/2015-02-03/#Ruby-VM
and
https://docs.travis-ci.com/user/languages/ruby/#Supported-Ruby-Versions-and-RVM

Follows on work in https://github.com/rails/rails/pull/23927 which was reverted
https://github.com/rails/rails/commit/26fe5fa08d52384bcea09c4210e3b3baaf5e9b95

JRUBY_OPTS minimize GC, disable JIT, for max test speed
  - https://github.com/rails/rails/pull/16613
  - https://github.com/rails/rails/pull/17088

Have Rails use JRuby-compatible Rake 11.1
  - The Rake task was passing --verbose, an invalid option, to contemporary JRuby
  - https://github.com/ruby/rake/pull/120
  - https://github.com/rails-api/active_model_serializers/pull/1585
  - https://github.com/jruby/jruby/issues/3653#issuecomment-195883717

No advantage to directly mounting JRuby over installing from cache; both on S3
  - https://github.com/rails/rails/pull/23499/commits/b2d5b336b5a812009444571b22eed90777cd9a8c
  - https://github.com/rails/rails/pull/23499/commits/f4fad041b2755d81e82ee3fc66d96f334b4653db

1 files changed, 1 insertions, 1 deletions

diff --git a/Gemfile b/Gemfile
index dd09ddae68..5205896846 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,7 +3,7 @@ source 'https://rubygems.org'
 gemspec
 
 # We need a newish Rake since Active Job sets its test tasks' descriptions.
-gem 'rake', '>= 10.3'
+gem 'rake', '>= 11.1'
 
 # This needs to be with require false to ensure correct loading order, as it has to
 # be loaded after loading the test library.