Merge branch 'v1.x' of https://github.com/gabime/spdlog into v1.x

appveyor.yml

 version: 1.0.{build}
-image: Visual Studio 2015
+image: Visual Studio 2017
 environment:
   matrix:
   - GENERATOR: '"MinGW Makefiles"'
@@ -14,6 +14,10 @@ environment:
     BUILD_TYPE: Debug
   - GENERATOR: '"Visual Studio 14 2015 Win64"'
     BUILD_TYPE: Release
+  - GENERATOR: '"Visual Studio 15 2017 Win64"'
+    BUILD_TYPE: Debug
+  - GENERATOR: '"Visual Studio 15 2017 Win64"'
+    BUILD_TYPE: Release
 build_script:
 - cmd: >-
     set
@@ -24,7 +28,7 @@ build_script:
 
     set PATH=%PATH:C:\Program Files\Git\usr\bin;=%
 
-    set PATH=C:\mingw-w64\i686-5.3.0-posix-dwarf-rt_v4-rev0\mingw32\bin;%PATH%
+    set PATH=C:\mingw-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1;%PATH%
 
     cmake .. -G %GENERATOR% -DCMAKE_BUILD_TYPE=%BUILD_TYPE% -DSPDLOG_WCHAR_SUPPORT=ON -DSPDLOG_BUILD_EXAMPLE=ON -DSPDLOG_BUILD_EXAMPLE_HO=ON -DSPDLOG_BUILD_TESTS=ON -DSPDLOG_BUILD_TESTS_HO=OFF