Update Travis config to use node v8

kunalkapadia · kunalkapadia · commit 2aea61cf5729 · 2018-03-23T12:53:56.000+05:30
diff --git a/.travis.yml b/.travis.yml
@@ -1,8 +1,6 @@
 language: node_js
 node_js:
-  - "4.8"
-  - "6.10"
-  - "7.6"
+  - "8.2"
 services:
   - mongodb
 cache:
