Auto merge of #47 - mbrubeck:travis, r=emilio

Re-enable cargo bench on Travis

This reverts commit 0586430 which disabled `cargo bench` on Travis because of #44  which is now fixed.

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.travis.yml

@@ -7,6 +7,7 @@ script: |
   cargo build --verbose &&
   cargo build --features=heapsizeof --verbose &&
   cargo test --verbose &&
-  cargo test --features=heapsizeof --verbose
+  cargo test --features=heapsizeof --verbose &&
+  ([ $TRAVIS_RUST_VERSION != nightly ] || cargo bench --verbose bench)
 notifications:
   webhooks: http://build.servo.org:54856/travis