Use nvm to install node on Travis CI

Author: sheabunge

.travis.yml

@@ -11,9 +11,6 @@ php:
 services:
   - mysql
 
-node_js:
-  - node
-
 env:
   global:
     - WP_DEVELOP_DIR=/tmp/wordpress/
@@ -30,6 +27,7 @@ env:
 # Prepare the system by installing prerequisites and dependencies.
 # Failures in this section will result in build status 'errored'.
 before_install:
+  - nvm install node
   - composer self-update
   - npm install -g gulp