Cleanup appveyor script

appveyor.yml

@@ -1,30 +1,17 @@
-# This is a comment.
-
-version: build.{build}
-
-os: Windows Server 2012 R2
-
 clone_folder: c:\projects\jsoncpp
 
-platform:
-    - Win32
-    - x64
+environment:
+  matrix:
+    - CMAKE_GENERATOR: Visual Studio 12 2013
+    - CMAKE_GENERATOR: Visual Studio 12 2013 Win64
+    - CMAKE_GENERATOR: Visual Studio 14 2015
+    - CMAKE_GENERATOR: Visual Studio 14 2015 Win64
 
-configuration:
-    - Debug
-    - Release
-
-# scripts to run before build
-before_build:
-    - echo "Running cmake..."
-    - cd c:\projects\jsoncpp
-    - cmake --version
-    - set PATH=C:\Program Files (x86)\MSBuild\14.0\Bin;%PATH%
-    - if %PLATFORM% == Win32 cmake .
-    - if %PLATFORM% == x64 cmake -G "Visual Studio 12 2013 Win64" .
-
-build:
-    project: jsoncpp.sln        # path to Visual Studio solution or project
+build_script:
+  - cmake --version
+  - cd c:\projects\jsoncpp
+  - cmake -G "%CMAKE_GENERATOR%" -DCMAKE_INSTALL_PREFIX=%CD:\=/%/install -DCMAKE_BUILD_TYPE=Release .
+  - cmake --build . --config Release --target install
 
 deploy:
     provider: GitHub