Lower number of Appveyor jobs

appveyor.yml

@@ -5,16 +5,17 @@ branches:
     - develop
     - master
 
-image:
-  - Visual Studio 2013
-  - Visual Studio 2015
-  - Visual Studio 2017
-
 environment:
   matrix:
-    - SCRIPT: ci_boost_status
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2013
+      SCRIPT: ci_boost_test_library
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      SCRIPT: ci_boost_test_library
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      SCRIPT: ci_boost_test_library
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      SCRIPT: ci_boost_status
       TARGET: quick
-    - SCRIPT: ci_boost_test_library
 
 init:
   - cd %APPVEYOR_BUILD_FOLDER%/..