Fix AppVeyor build

Jusonex · web-flow · commit dc4dd043df5b · 2017-03-25T11:26:20.000+01:00
See http://help.appveyor.com/discussions/problems/6312-curl-command-not-found
diff --git a/appveyor.yml b/appveyor.yml
@@ -5,6 +5,7 @@ configuration:
   - Release
 
 before_build:
+  - choco install curl
   - utils\premake5 install_cef
   - utils\premake5 vs2015
 
