Fix up the .travis.yml file

.travis.yml

@@ -1,15 +1,24 @@
 language: rust
-sudo: 9000
-dist: trusty
 rust:
   - nightly
 os:
   - linux
   - osx
 
+addons:
+  apt:
+    sources:
+    - ubuntu-toolchain-r-test
+    packages:
+    - gcc-4.8
+    - g++-4.8
+
 env:
-  - FEATURES=""
-  - FEATURES="--features debugmozjs"
+  global:
+    - CC="gcc-4.8" CPP="gcc-4.8 -E" CXX="g++-4.8"
+  matrix:
+    - FEATURES=""
+    - FEATURES="--features debugmozjs"
 
 before_install:
 - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install ccache; fi
@@ -20,9 +29,6 @@ script:
   - CCACHE=$(which ccache) cargo test --verbose $FEATURES
   - ccache -s
 
-branches:
-  except:
-    - master
 notifications:
   webhooks: http://build.servo.org:54856/travis