try out appveyor

appveyor.yml

@@ -0,0 +1,10 @@
+image: Visual Studio 2017
+
+build_script:
+  - cmd: mkdir tmp
+  - cmd: cd tmp
+  - cmd: cmake -G "Visual Studio 2017" ..
+
+test_script:
+  - cmd: cd tmp
+  - ctest -VV -C "Release"