use the gradle wrapper for appveyor builds and cache the dependencies

Author: johnscancella

appveyor.yml

@@ -1,21 +1,16 @@
 ---
 version: "{build}"
 
-init:
-  - ps: iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/appveyor/ci/master/scripts/enable-rdp.ps1'))
-
 install:
-- cmd: choco install gradle
 - cmd: git clone --depth 3 https://github.com/loc-rdc/bagit-conformance-suite.git
 
 build_script:
-- cmd: gradle check --no-daemon
+- cmd: ./gradlew.bat check --no-daemon
 
 shallow_clone: true
 
 cache:
-  - C:\ProgramData\chocolatey\bin -> appveyor.yml
-  - C:\ProgramData\chocolatey\lib -> appveyor.yml
+  - '%USERPROFILE%\.gradle\caches'
 
 notifications:
 - provider: Email