Upgrade travis testing to PhantomJS 2.1.1.

.travis.yml

@@ -7,6 +7,7 @@ cache:
   directories:
     - $HOME/.npm
     - $HOME/.yarn-cache
+    - travis_phantomjs
 
 env:
   global:
@@ -30,6 +31,18 @@ branches:
     - master
 
 before_install:
+  # Upgrade PhantomJS.
+  - |
+      export PHANTOMJS_VERSION=2.1.1
+      export PATH=$PWD/travis_phantomjs/phantomjs-$PHANTOMJS_VERSION-linux-x86_64/bin:$PATH
+      if [ $(phantomjs --version) != $PHANTOMJS_VERSION ]; then
+        rm -rf $PWD/travis_phantomjs
+        mkdir -p $PWD/travis_phantomjs
+        wget https://github.com/Medium/phantomjs/releases/download/v$PHANTOMJS_VERSION/phantomjs-$PHANTOMJS_VERSION-linux-x86_64.tar.bz2
+        tar -xvf phantomjs-$PHANTOMJS_VERSION-linux-x86_64.tar.bz2 -C $PWD/travis_phantomjs
+      fi
+      phantomjs -v
+
   # Use exact Node version.
   - nvm use $TRAVIS_NODE_VERSION