travis: go with stock

Author: iarna

.travis.yml

@@ -5,16 +5,4 @@ node_js:
   - "6"
   - "7"
   - "4"
-before_install:
-  - "npm config set spin false"
-  - "ls .npm-bin/bin/npm > /dev/null 2>&1 || npm install --prefix .npm-bin -g npm"
-install:
-  - ".npm-bin/bin/npm prune"
-  - ".npm-bin/bin/npm install"
 sudo: false
-script: ".npm-bin/bin/npm test"
-cache:
-  directories:
-  - .npm-bin
-  - $HOME/.npm
-  - node_modules