Add appveyor

appveyor.yml

@@ -0,0 +1,18 @@
+platform:
+  - x64
+
+cache:
+  - node_modules
+  - '%LOCALAPPDATA%\electron\Cache'
+
+install:
+  - set PATH=C:\Ruby23-x64\bin;%PATH%
+  - ps: Install-Product node 6 x64
+  - gem install sass
+  - yarn install
+
+test_script:
+  - yarn test
+
+build_script:
+  - yarn travis-build