Modernize the AppVeyor setup

appveyor.yml

@@ -1,6 +1,14 @@
 environment:
   matrix:
+  - JULIA_URL: "https://julialang-s3.julialang.org/bin/winnt/x86/0.6/julia-0.6-latest-win32.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/x86/julia-latest-win32.exe"
+  - JULIA_URL: "https://julialangnightlies-s3.julialang.org/bin/winnt/x64/julia-latest-win64.exe"
+
+branches:
+  only:
+    - master
+    - /release-.*/
 
 notifications:
   - provider: Email
@@ -10,6 +18,11 @@ notifications:
 
 install:
   - ps: "[System.Net.ServicePointManager]::SecurityProtocol = [System.Net.SecurityProtocolType]::Tls12"
+# if there's a newer build queued for the same PR, cancel this one
+  - ps: if ($env:APPVEYOR_PULL_REQUEST_NUMBER -and $env:APPVEYOR_BUILD_NUMBER -ne ((Invoke-RestMethod `
+        https://ci.appveyor.com/api/projects/$env:APPVEYOR_ACCOUNT_NAME/$env:APPVEYOR_PROJECT_SLUG/history?recordsNumber=50).builds | `
+        Where-Object pullRequestId -eq $env:APPVEYOR_PULL_REQUEST_NUMBER)[0].buildNumber) { `
+        throw "There are newer queued builds for this pull request, failing early." }
 # Download most recent Julia Windows binary
   - ps: (new-object net.webclient).DownloadFile(
         $env:JULIA_URL,
@@ -24,4 +37,4 @@ build_script:
       Pkg.clone(pwd(), \"DeepDiffs\"); Pkg.build(\"DeepDiffs\")"
 
 test_script:
-  - C:\projects\julia\bin\julia -e "Pkg.test(\"DeepDiffs\")"
+  - C:\projects\julia\bin\julia --check-bounds=yes -e "Pkg.test(\"DeepDiffs\")"