Improve appveyor.yml (#5)

* Update appveyor.yml

* Update appveyor.yml

Author: gengjiawen

appveyor.yml

@@ -1,4 +1,6 @@
 version: 1.0.{build}
+image:
+- Visual Studio 2017
 
 platform:
   - x64
@@ -7,15 +9,11 @@ init:
   - git config --global core.autocrlf input
 
 install:
-  - ps: Install-Product node 8 x64
-  - git reset --hard HEAD
-  - npm install npm -g
+  - ps: Install-Product node stable x64
   - npm install
-  - npm prune
 
 build_script:
-  - node --version
-  - npm --version
+  - npx envinfo
   - npm run dist
 
-test: off
+test: off