enable AppVeyor CI

appveyor.yml

@@ -2,23 +2,19 @@ environment:
   matrix:
     - nodejs_version: "0.10"
     - nodejs_version: "0.12"
-  - nodejs_version: "4.0"
-  - nodejs_version: "6.0"
-
+    - nodejs_version: "4"
+    - nodejs_version: "6"
+    - nodejs_version: "8"
+install:
+  - ps: Install-Product node $env:nodejs_version
+  - set UGLIFYJS_TEST_ALL=1
+  - npm install
+build: off
+cache:
+  - tmp
 matrix:
   fast_finish: true
-
-platform:
-  - x86
-  - x64
-
-install:
-  - ps: Install-Product node $env:nodejs_version $env:platform
-  - npm install
-
 test_script:
   - node --version
   - npm --version
   - npm test
-
-build: off