Drop Node 6 from Travis and Appveyor

Author: kristerkari

.travis.yml

@@ -20,9 +20,6 @@ matrix:
     - node_js: "8"
       script: npm test
       env: CI=test
-    - node_js: "6"
-      script: npm test
-      env: CI=tests 6
 before_install:
   - npm install -g npm@latest
 after_success:

appveyor.yml

@@ -5,7 +5,6 @@ environment:
     - nodejs_version: 11
     - nodejs_version: 10
     - nodejs_version: 8
-    - nodejs_version: 6
 
 version: "{build}"
 build: off