fix Travis warnings

Author: korny

.travis.yml

@@ -3,6 +3,7 @@ env:
     - "JRUBY_OPTS=-Xcext.enabled=true"
     - "CC_TEST_REPORTER_ID=faa393209ff0a104cf37511a9a03510bcee37951971b1ca4ffc2af217851d47e"
 language: ruby
+os: linux
 rvm:
   - 1.8.7
   - ree
@@ -18,7 +19,7 @@ rvm:
   - 3.0
   - ruby-head
   - jruby
-matrix:
+jobs:
   allow_failures:
     - rvm: 1.8.7
     - rvm: ree
@@ -35,4 +36,3 @@ before_script:
 script: "rake test" # test:scanners"
 after_script:
   - ./cc-test-reporter after-build --exit-code $TRAVIS_TEST_RESULT
-sudo: false