Include PowerShell completion script in release

See #64

appveyor.yml

@@ -56,8 +56,8 @@ before_deploy:
   # Generate artifacts for release
   - cargo build --release
   - mkdir staging
-  # TODO update this part to copy the artifacts that make sense for your project
   - copy target\release\fd.exe staging
+  - copy target\release\build\fd-find-*\out\_fd.ps1 staging
   - cd staging
     # release zipfile will look like 'rust-everywhere-v1.2.3-x86_64-pc-windows-msvc'
   - 7z a ../%PROJECT_NAME%-%APPVEYOR_REPO_TAG_NAME%-%TARGET%.zip *