switched VS build to debug in the hope of improving compilation times and go below the 60 minutes appveyor limit

Former-commit-id: bf80cfaafeae0edb60019ae8b949be49d36d3f92

.appveyor.yml

@@ -14,6 +14,8 @@ build_script:
   - mkdir build
   - cd build
   - cmake -D "LIBIGL_USE_STATIC_LIBRARY=ON" -G "Visual Studio 14 2015 Win64" ../
+#  - cmake -G "Visual Studio 14 2015 Win64" ../
   - set MSBuildLogger="C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll"
-  - set MSBuildOptions=/v:m /p:Configuration=Release /logger:%MSBuildLogger%
+#  - set MSBuildOptions=/v:m /p:Configuration=Release /logger:%MSBuildLogger%
+  - set MSBuildOptions=/v:m /p:Configuration=Debug /logger:%MSBuildLogger%
   - msbuild %MSBuildOptions% libigl_tutorials.sln