Don't define CHROME env variable on Travis

Author: marco-c

.travis.yml

@@ -7,8 +7,8 @@ env:
     - MOZ_XVFB=$(if [[ $TRAVIS_OS_NAME == "linux" ]]; then echo 1; fi)
   matrix:
     - NODE_VERSION="0.12"
-    - NODE_VERSION="4" CHROME="nightly"
-    - NODE_VERSION="stable" CHROME="nightly"
+    - NODE_VERSION="4"
+    - NODE_VERSION="stable"
 before_install:
   - rm -rf ~/.nvm
   - git clone https://github.com/creationix/nvm.git ~/.nvm && (cd ~/.nvm && git checkout `git describe --abbrev=0 --tags`)