chore: update CI for current Node LTS

Author: Audrey Eschright

.travis.yml

@@ -4,9 +4,7 @@ before_install:
   - "npm config set spin false"
   - "npm install -g npm"
 node_js:
-  - "5"
-  - "4"
-  - iojs
-  - "0.12"
-  - "0.10"
-  - "0.8"
+  - "10"
+  - "8"
+  - "6"
+  - "11"