Add Visual Studio 2017 in AppVeyor CI.

Author: Tessil

appveyor.yml

@@ -1,25 +1,40 @@
-os: Visual Studio 2015
+environment:
+    BOOST_ROOT: C:\Libraries\boost_1_67_0
+    matrix:
+        - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+          ARCH: Win32
+          BOOST_LIBRARYDIR: C:\Libraries\boost_1_67_0\lib32-msvc-14.0
+          CMAKE_GENERATOR: Visual Studio 14 2015
 
-platform:
-  - Win32
-  - x64
+        - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+          ARCH: x64
+          BOOST_LIBRARYDIR: C:\Libraries\boost_1_67_0\lib64-msvc-14.0
+          CMAKE_GENERATOR: Visual Studio 14 2015 Win64
+
+        - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+          ARCH: Win32
+          BOOST_LIBRARYDIR: C:\Libraries\boost_1_67_0\lib32-msvc-14.1
+          CMAKE_GENERATOR: Visual Studio 15 2017
+          CXXFLAGS: /permissive-
+
+        - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+          ARCH: x64
+          BOOST_LIBRARYDIR: C:\Libraries\boost_1_67_0\lib64-msvc-14.1
+          CMAKE_GENERATOR: Visual Studio 15 2017 Win64
+          CXXFLAGS: /permissive-
 
 configuration:
-  - Debug
-  - Release
-  
+    - Debug
+    - Release
+
 build_script:
-  - set BOOST_ROOT=C:\Libraries\boost_1_62_0
-  - if %PLATFORM% == Win32 set BOOST_LIBRARYDIR=C:\Libraries\boost_1_62_0\lib32-msvc-14.0
-  - if %PLATFORM% == x64 set BOOST_LIBRARYDIR=C:\Libraries\boost_1_62_0\lib64-msvc-14.0
-  - cd tests
-  - mkdir build
-  - cd build
-  - if %PLATFORM% == Win32 cmake .. -G"Visual Studio 14 2015"
-  - if %PLATFORM% == x64 cmake .. -G"Visual Studio 14 2015 Win64"
-  - cmake --build . --config %CONFIGURATION%
-  
+    - cd tests
+    - mkdir build
+    - cd build
+    - cmake .. -G"%CMAKE_GENERATOR%"
+    - cmake --build . --config %CONFIGURATION%
+
 test_script: 
-  - set PATH=%PATH%;%BOOST_LIBRARYDIR%
-  - .\%CONFIGURATION%\tsl_hopscotch_map_tests.exe
+    - set PATH=%PATH%;%BOOST_LIBRARYDIR%
+    - .\%CONFIGURATION%\tsl_hopscotch_map_tests.exe