Auto merge of #47 - nox:travis-osx, r=frewsxcv

Test OS X on Travis

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Author: bors-servo

.travis.yml

@@ -8,6 +8,10 @@ rust:
  - beta
  - stable
 
+os:
+  - linux
+  - osx
+
 notifications:
   webhooks: http://build.servo.org:54856/travis