Update Travis script

.travis.yml

@@ -1,23 +1,30 @@
 sudo: false
 language: node_js
+cache:
+  directories:
+    - node_modules
+notifications:
+  email: false
 node_js:
-  - 0.10
   - 0.12
-  - 4.4
+  - 4
-  - 5.8
+  - 5
+  - 6
 matrix:
+    fast_finish: true
     allow_failures:
-        - node_js: 4.4
+        - node_js: 6
-        - node_js: 5.8
 env:
   global:
     - CXX=g++-4.8
-  matrix:
+script: "npm run travis"
-    - TEST_SUITE=unit
-script: "npm run $TEST_SUITE"
 addons:
   apt:
     sources:
       - ubuntu-toolchain-r-test
     packages:
       - g++-4.8
+before_install:
+  - npm i -g npm@^2.0.0
+before_script:
+  - npm prune