test: add .appveyor.yml

Refs: metarhia/jstp#260 (comment)
PR-URL: metarhia/jstp#261
Reviewed-By: Dmytro Nechai <nechaido@gmail.com>

.appveyor.yml

@@ -0,0 +1,27 @@
+image: Visual Studio 2015
+
+environment:
+  matrix:
+    - nodejs_version: 6
+    - nodejs_version: 8
+
+platform:
+  - x86
+  - x64
+
+version: '{build}'
+
+branches:
+  only:
+    - master
+
+install:
+  - ps: Install-Product node $env:nodejs_version
+  - npm install
+
+build: off
+
+test_script:
+  - node --version
+  - npm --version
+  - npm test