Merge pull request #799 from ruby-concurrency/pitr-ch-patch-1

Update truffleruby in CI

Author: pitr-ch

.travis.yml

@@ -17,13 +17,7 @@ matrix:
       rvm: jruby-9.2.5.0
       jdk: oraclejdk8
     - name: TruffleRuby Latest
-      rvm: system
-      install:
-        - export TRUFFLERUBY_VERSION=1.0.0-rc8
-        - curl -L https://github.com/oracle/truffleruby/releases/download/vm-$TRUFFLERUBY_VERSION/truffleruby-$TRUFFLERUBY_VERSION-linux-amd64.tar.gz | tar xz
-        - export PATH="$PWD/truffleruby-$TRUFFLERUBY_VERSION-linux-amd64/bin:$PATH"
-        - gem install bundler
-        - bundle install
+      rvm: truffleruby
     - name: YARD uptodate in docs
       rvm: 2.6.0
       script: