[appveyor] Update VS version to 2017

It seems like VS 2015 may be generating bad code (see #20). Let's try
using 2017 instead.

Also, include SDL2.dll with the Windows bundles.

README.md

@@ -82,7 +82,7 @@ When building on Windows, you'll probably have to set the SDL2 directory:
 ```
 > mkdir build
 > cd build
-> cmake .. -G "Visual Studio 14 2015" -DSDL2_ROOT_DIR="C:\path\to\SDL\"
+> cmake .. -G "Visual Studio 15 2017" -DSDL2_ROOT_DIR="C:\path\to\SDL\"
 ```
 
 Then load this solution into Visual Studio and build it. Make sure to build the

appveyor.yml

@@ -1,3 +1,5 @@
+image: Visual Studio 2017
+
 install:
   - git submodule update --init
 
@@ -6,18 +8,21 @@ environment:
   SDL2_DOWNLOAD_DIR: c:\sdl2
   SDL2_ROOT_DIR: c:\sdl2\SDL2-2.0.5
   matrix:
-    - GENERATOR: Visual Studio 14 2015
+    - GENERATOR: Visual Studio 15 2017
       CONFIG: Release
       DEPLOY: true
       DEPLOY_NAME: binjgb-win32.zip
-    - GENERATOR: Visual Studio 14 2015 Win64
+      SDL_DLL_PATH: lib\x86\SDL2.dll
+    - GENERATOR: Visual Studio 15 2017 Win64
       CONFIG: Debug
       DEPLOY: false
       DEPLOY_NAME: binjgb-win64.zip
-    - GENERATOR: Visual Studio 14 2015 Win64
+      SDL_DLL_PATH: lib\x64\SDL2.dll
+    - GENERATOR: Visual Studio 15 2017 Win64
       CONFIG: Release
       DEPLOY: true
       DEPLOY_NAME: binjgb-win64.zip
+      SDL_DLL_PATH: lib\x64\SDL2.dll
 
 build_script:
   - cmake --version
@@ -30,7 +35,7 @@ build_script:
   - cmake --build . --config %CONFIG%
 
 after_build:
-  - 7z a %DEPLOY_NAME% %APPVEYOR_BUILD_FOLDER%\%CONFIG%\binjgb*.exe
+  - 7z a %DEPLOY_NAME% %APPVEYOR_BUILD_FOLDER%\%CONFIG%\binjgb*.exe %SDL2_ROOT_DIR%\%SDL_DLL_PATH%
 
 artifacts:
   - path: "%DEPLOY_NAME%"