remove EOL node versions and use bundled npm version

appveyor.yml

@@ -15,9 +15,7 @@ environment:
   matrix:
     - nodejs_version: "9"
     - nodejs_version: "8"
-    - nodejs_version: "7"
     - nodejs_version: "6"
-    - nodejs_version: "5"
     - nodejs_version: "4"
 
 # Build on both platforms
@@ -29,9 +27,6 @@ platform:
 install:
   # Get the latest version of $env:nodejs_version
   - ps: Update-NodeJsInstallation (Get-NodeJsLatestBuild $env:nodejs_version) $env:platform
-  # Update to latest npm
-  - npm -g install npm 2>&1>nul
-  - SET PATH=%APPDATA%\npm;%PATH%
   # Output useful info for debugging
   - node --version
   - npm --version