Update CI URLs to point to new caching infrastructure

appveyor.yml

@@ -1,6 +1,6 @@
 environment:
   matrix:
-  - JULIAVERSION: "julialang/bin/winnt/x64/0.5/julia-0.5-latest-win64.exe"
+  - JULIA_URL: "https://julialang-s3.julialang.org/bin/winnt/x64/0.5/julia-0.5-latest-win64.exe"
 
 branches:
   only:
@@ -14,9 +14,10 @@ notifications:
     on_build_status_changed: false
 
 install:
+  - ps: "[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12"
 # Download most recent Julia Windows binary
   - ps: (new-object net.webclient).DownloadFile(
-        $("http://s3.amazonaws.com/"+$env:JULIAVERSION),
+        $env:JULIA_URL,
         "C:\projects\julia-binary.exe")
 # Run installer silently, output to C:\projects\julia
   - C:\projects\julia-binary.exe /S /D=C:\projects\julia