Update AppVeyor script

Author: claudiofantacci

.appveyor.yml

@@ -1,31 +1,50 @@
+# AppVeyor is very similar to travis, with some differences to comply with
+# MS Windows builds. See https://www.appveyor.com/docs/build-configuration/
+# for the full documentation of the a build configuration script. See
+# https://www.appveyor.com/docs/appveyor-yml/ for a complete appveyor.yml
+# full syntax reference.
+
 version: 1.0.{build}
 
 clone_folder: c:\dev\lib-template-cmake
 
-os:
-  - Visual Studio 2013
-  - Visual Studio 2015
-  - Visual Studio 2017
+environment:
+  matrix:
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      CMAKE_GENERATOR: "Visual Studio 14 2015"
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      CMAKE_GENERATOR: "Visual Studio 14 2015 Win64"
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      CMAKE_GENERATOR: "Visual Studio 15 2017"
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      CMAKE_GENERATOR: "Visual Studio 15 2017 Win64"
+
+init:
+    # Print some more system information after installing all build tools
+    - ps: echo "-------------------- BEGIN SYSTEM INFORMATION --------------------"
+    - ps: echo $env:CMAKE_GENERATOR
+    - ps: cmake --version
+    - ps: echo "--------------------  END SYSTEM INFORMATION  --------------------"
 
 install:
 
 build:
 
 build_script:
   # Build the library
-  - cd c:\dev\lib-template-cmake
-  - md build
-  - cd build
-  - cmake -DBUILD_TESTING:BOOL=ON -DCMAKE_CXX_FLAGS:STRING="/W4" ..
+  - ps: cd c:\dev\lib-template-cmake
+  - ps: md build
+  - ps: cd build
+  - ps: cmake -G"$env:CMAKE_GENERATOR" -DBUILD_TESTING:BOOL=ON -DCMAKE_CXX_FLAGS:STRING="/W4" ..
 
   # Build the library for Release and Debug
-  - cmake --build . --config Debug
-  - cmake --build . --config Release
+  - ps: cmake --build . --config Debug
+  - ps: cmake --build . --config Release
 
 after_build:
   # Install only release
-  - cmake --build C:\dev\lib-template-cmake\build --config Release --target INSTALL
+  - ps: cmake --build C:\dev\lib-template-cmake\build --config Release --target INSTALL
 
 test_script:
-  - ctest -C Debug -VV
-  - ctest -C Release -VV
+  - ps: ctest -C Debug -VV
+  - ps: ctest -C Release -VV