Auto merge of #346 - nox:backcompat, r=nox

Build with Rust 1.13 on Travis

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Author: bors-servo

.travis.yml

@@ -3,6 +3,7 @@ rust:
   - nightly
   - beta
   - stable
+  - 1.15.0
 script: make test
 notifications:
   webhooks: http://build.servo.org:54856/travis