Merge pull request #1 from silvermine/update_travis_versions

Update Travis CI node versions

.travis.yml

@@ -1,9 +1,13 @@
 language: node_js
 node_js:
+  - "node" # Latest node version
+  - "lts/*" # Latest LTS version
+  - "10"
+  - "8"
   - "8.10"
-  - "6.10"
+  - "6"
 
-before_install: if [[ `npm -v` != 6* ]]; then npm i -g npm@6; fi
+before_install: if [[ `npm -v` != 6* ]]; then npm i -g npm@6.4.1; fi
 
 script:
    - node --version