fix(travis): use phantom 2

.travis.yml

@@ -1,4 +1,19 @@
+---
 language: node_js
+
+cache:
+  directories:
+    - node_modules
+
+before_install:
+  - mkdir travis-phantomjs
+  - wget https://bitbucket.org/ariya/phantomjs/downloads/phantomjs-2.1.1-linux-x86_64.tar.bz2 -O $PWD/travis-phantomjs/phantomjs-2.1.1-linux-x86_64.tar.bz2
+  - tar -xvf $PWD/travis-phantomjs/phantomjs-2.1.1-linux-x86_64.tar.bz2 -C $PWD/travis-phantomjs
+  - export PATH=$PWD/travis-phantomjs/phantomjs-2.1.1-linux-x86_64/bin:$PATH
+
+install:
+  - npm install
+
 script: npm test
 after_success:
 - npm build
@@ -9,3 +24,4 @@ env:
   - secure: Lo7dEbRFHNrQL29iUs88zFQyRNWcK7lnLIoPlBIUDiLOXamsUilxykAPmifIK34yFS4GqN+zv9mkcVEkieRQV5LlZgNd1RLJ5nDM6bkMSRM1K14K36EUy3ldU9Ld1d/sa5yx4cxJXqNRjfF/d+i7OTDQduLYmrFLhLPPu2HetbA=
   - secure: cAsSmFA77dBTgo7JHT3kcXlwAfilDoOwrVo3b77SHj64rWVUjB3xyaCWY+3gCoULTDD/fuEO80TWwzfV2sQGASvJyrSNLw3P7//Ym/dkHcTdQ3CfCagCf689/PfFTMM1+v6gZHSYcryJzRWkLolEgFlkU+lw4rwVlRjrKSwnRgQ=
   - secure: bNBRMlxWFRbAR04OI1SfwfYJis9KTm0C6O/xkAuMiardqJ6z+EpTXKSplAu6MlUM5VsiOON2ZNwo3bwmtshWhGiUhOVnjZCBtuVcJXyj/RQk9ug8A8pFKYn4o3Yn57H6o4tj/Gw3/NV5ocbw5MzRbgCSFkLbHl9lPDRTYyX2SwM=
+