Node >= v8.0.0 support for web3 1.0

Helps with #2913

Author: michaelsbradleyjr

.travis.yml

@@ -3,6 +3,7 @@ node_js:
     - "8"
     - "10"
     - "11"
+    - "12"
 env:
     - CXX=g++-4.8
 addons:
@@ -21,4 +22,3 @@ script:
     - npm run-script test-coveralls
 after_script:
     - cd test/node && npm install && node app.js
-