Simplify the Travis CI setup

.travis.yml

@@ -1,30 +1,14 @@
-addons:
-  apt:
-    sources:
-      - ubuntu-toolchain-r-test
-    packages:
-      - libstdc++-4.9-dev
-
-language: generic
+language: node_js
 
 matrix:
   fast_finish: true
 
-env:
-  matrix:
-    - NODEJS_VER=node/6
-    - NODEJS_VER=node/8
-    - NODEJS_VER=node/10
-    - NODEJS_VER=node/latest
-
-before_install:
-  - git clone --branch v1.4.2 --depth 1 https://github.com/jasongin/nvs.git ~/.nvs
-  - . ~/.nvs/nvs.sh
-  - nvs --version
+node_js:
+  - "10"
+  - "12"
+  - "node"
 
 install:
-  - nvs add $NODEJS_VER
-  - nvs use $NODEJS_VER
   - node --version
   - npm --version --no-update-notifier
   - npm install --no-optional --no-save --no-update-notifier
@@ -33,4 +17,4 @@ script:
   - npm test --no-update-notifier
 
 notifications:
-  email: false
+  email: false