Auto merge of #310 - emilio:travis, r=<try>

Potentially fix travis build.

r? @Ms2ger

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Author: bors-servo

.travis.yml

@@ -12,7 +12,7 @@ env:
   - FEATURES="--features debugmozjs"
 
 before_install:
-- if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install ccache; fi
+- if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install ccache yasm; fi
 
 script:
   - ccache -z