update appveyor

Author: SimonDanisch

appveyor.yml

@@ -1,8 +1,11 @@
 environment:
   matrix:
-  - JULIAVERSION: "julianightlies/bin/winnt/x64/julia-latest-win64.exe"
-  - JULIAVERSION: "julialang/bin/winnt/x64/0.5/julia-0.5-latest-win64.exe"
-
+  - JULIA_URL: "https://julialang-s3.julialang.org/bin/winnt/x64/0.6/julia-0.6-latest-win64.exe"
+  - JULIA_URL: "https://julialangnightlies-s3.julialang.org/bin/winnt/x64/julia-latest-win64.exe"
+matrix:
+  allow_failures:
+  - JULIA_URL: "https://julialangnightlies-s3.julialang.org/bin/winnt/x64/julia-latest-win64.exe"
+  
 branches:
   only:
     - master