Have AppVeyor install Win32::ShellQuote

Per recommendation from David Wheeler in
pjf#29 (comment)

Author: jkeenan

.appveyor.yml

@@ -12,7 +12,8 @@ install:
   - if not exist "C:\strawberry" cinst strawberryperl
   - set PATH=C:\strawberry\perl\bin;C:\strawberry\perl\site\bin;C:\strawberry\c\bin;%PATH%
   - cd C:\projects\%APPVEYOR_PROJECT_NAME%
-  - cpanm --installdeps .
+  - cpanm --verbose Win32::ShellQuote
+  - cpanm --verbose --installdeps .
 
 build_script:
   - perl Makefile.PL