Install nodejs & jshint on travis

.travis.yml

@@ -6,5 +6,15 @@ go:
 
 go_import_path: github.com/cloudflare/unsee
 
+# nodejs is needed so that we can install jshint
+addons:
+  apt:
+    packages:
+      - nodejs
+
+# install jshint, it's used for linting js files (needs nodejs)
+before_script:
+  - npm install jshint
+
 script:
   - make test