Update CI to build against node 10

Author: Zane Starr

.travis.yml

@@ -4,12 +4,8 @@ language: node_js
 
 matrix:
   include:
-  - node_js: 6
+  - node_js: 10
     env: CXX=g++-4.8
-  - node_js: 8
-    env: CXX=g++-4.8
-    #  - node_js: stable
-    #    env: CXX=g++-4.8
 
 script:
   - npm run lint