remove outdated node.js version, add latest ones

Author: sokra

.travis.yml

@@ -4,9 +4,10 @@ os:
   - linux
   - osx
 node_js:
+  - "12"
+  - "10"
   - "8"
   - "6"
-  - "4"
 
 script: npm run travis
 

appveyor.yml

@@ -7,9 +7,10 @@ init:
 # what combinations to test
 environment:
   matrix:
+    - nodejs_version: 12
+    - nodejs_version: 10
     - nodejs_version: 8
     - nodejs_version: 6
-    - nodejs_version: 4
 
 install:
   - ps: Install-Product node $env:nodejs_version x64