enable dep pruning and gitignore macOS DS_Store

.gitignore

@@ -14,3 +14,6 @@ kustomize
 
 # We use sed -i.bak when doing in-line replace, because it works better cross-platform
 .bak
+
+# macOS
+*.DS_store

Gopkg.toml

@@ -20,6 +20,11 @@
 #  name = "github.com/x/y"
 #  version = "2.4.0"
 
+# prune out unused content from vendor
+[prune]
+  go-tests = true
+  non-go = true
+  unused-packages = true
 
 [[constraint]]
   name = "github.com/evanphx/json-patch"