another try

CMakeLists.txt

+cmake_minimum_required(VERSION 3.2)
+
+project(json CXX)
+
+add_executable(json_unit
+    src/json.hpp test/catch.hpp test/unit.cpp
+)
+
+target_compile_features(json_unit
+    PRIVATE cxx_range_for
+)
+
+include_directories(
+    src test
+)

appveyor.yml

+version: 1.0.{build}
+os: Visual Studio 2015 Preview
+init:
+- cmake -G "Visual Studio 14 2015 Win64"
+build:
+  verbosity: minimal