update travis.yml with new node versions

Author: AJ Keller

.travis.yml

@@ -1,22 +1,9 @@
 language: node_js
 node_js:
-  - "4.0"
-  - "4.1"
-  - "4.2"
-  - "4.3"
-  - "4.4"
-  - "4.5"
-  - "4.6"
-  - "5.11.0"
-  - "6.0"
-  - "6.1"
-  - "6.2"
-  - "6.3"
-  - "6.4"
-  - "6.5"
-  - "6.6"
-  - "6.7"
-  - "6.8"
+  - "4.8.4"
+  - "6.11.1"
+  - "7.10.1"
+  - "8.1.4"
 install:
   - npm install --all
 script: