set JRUBY_OPTS to global on .travis

Author: e2

.travis.yml

@@ -1,15 +1,11 @@
 sudo: false
 language: ruby
 bundler_args: --without development
+env: JRUBY_OPTS='--server -Xcompile.invokedynamic=false'
 rvm:
   - 2.2.5
   - 2.3.1
   - jruby-9.1.2.0
 
-matrix:
-  include:
-    - rvm: jruby-9.1.2.0
-      env: JRUBY_OPTS='--server -Xcompile.invokedynamic=false'
-
 before_install: gem install bundler -v 1.12.5
 cache: bundler