Update .travis.yml to build for Node 10

Author: daviwil

.travis.yml

@@ -14,6 +14,7 @@ language: node_js
 
 node_js:
   - "8"
+  - "10"
 
 env:
   - CC=clang CXX=clang++ npm_config_clang=1
@@ -22,4 +23,4 @@ script: npm test
 
 branches:
   only:
-    - master
+    - master