Updated travis config.

Author: neogeek

.travis.yml

@@ -1,12 +1,12 @@
 language: node_js
 node_js:
-  - "4"
-  - "5"
-  - "6"
-  - "7"
+    - '6'
+    - '8'
+    - '10'
+    - '11'
 before_install:
-  - if [[ `npm -v` != 3* ]]; then npm i -g npm@3; fi
-  - npm install doxdox -g
+    - if [[ `npm -v` != 6* ]]; then npm i -g npm@6; fi
+    - npm install doxdox -g
 after_success:
-  - npm run test:docs
+    - npm run test:docs
 sudo: false