Update appveyor rule to support VS2017.

Author: gongminmin

appveyor.yml

@@ -1,4 +1,3 @@
-os: Visual Studio 2015 CTP  
 version: 1.1.0.{build}
 
 configuration:
@@ -11,21 +10,35 @@ environment:
   #   VS_PLATFORM: win32
   # - VS_VERSION: 9 2008
   #   VS_PLATFORM: x64
-  - VS_VERSION: 10 2010
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+    VS_VERSION: 10 2010
     VS_PLATFORM: win32
-  - VS_VERSION: 10 2010
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+    VS_VERSION: 10 2010
     VS_PLATFORM: x64
-  - VS_VERSION: 11 2012
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+    VS_VERSION: 11 2012
     VS_PLATFORM: win32
-  - VS_VERSION: 11 2012
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+    VS_VERSION: 11 2012
     VS_PLATFORM: x64
-  - VS_VERSION: 12 2013
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+    VS_VERSION: 12 2013
     VS_PLATFORM: win32
-  - VS_VERSION: 12 2013
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+    VS_VERSION: 12 2013
     VS_PLATFORM: x64
-  - VS_VERSION: 14 2015
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+    VS_VERSION: 14 2015
     VS_PLATFORM: win32
-  - VS_VERSION: 14 2015
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+    VS_VERSION: 14 2015
+    VS_PLATFORM: x64
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+    VS_VERSION: 15 2017
+    VS_PLATFORM: win32
+  - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+    VS_VERSION: 15 2017
     VS_PLATFORM: x64
 
 before_build: