Update AppVeyor in attempt to fix failing tests

appveyor.yml

@@ -115,6 +115,13 @@ install:
   - "SET PATH=%cd%;%PATH%" # Add current working directory to PATH
   - where php-cs-fixer
 
+  # Docker
+  - choco install docker-for-windows --pre
+  - choco install docker
+  - where docker
+  - docker --version
+  - docker ps
+
   # Uncrustify
   - curl -k -L http://sourceforge.net/projects/uncrustify/files/uncrustify/uncrustify-0.61/uncrustify-0.61.3-gf65394e-win32.zip/download -o uncrustify.zip
   - cinst 7zip.commandline -y
@@ -123,22 +130,13 @@ install:
   - where uncrustify
 
   # elm-format
-  - curl -k -L https://github.com/avh4/elm-format/releases/download/0.7.0-exp/elm-format-0.17-0.7.0-exp-win-x64.zip -o elm-format.zip
-  - 7za e elm-format.zip -oelm-format-d
-  - "SET PATH=%cd%\\elm-format-d;%PATH%"
-  - where elm-format
+  - docker pull unibeautify/elm-format
+  - docker run -it unibeautify/elm-format
 
   # R
   - choco install r.project
   - where Rscript
 
-  # Docker
-  - choco install docker-for-windows --pre
-  - choco install docker
-  - where docker
-  - docker --version
-  - docker ps
-
   # Beautysh
   - docker pull unibeautify/beautysh
   - docker run -it unibeautify/beautysh