Makes directory pkg compilable on Windows.

Also makes the test cases platform independent.

Signed-off-by: Rick Wieman <git@rickw.nl>

directory/directory_windows.go

@@ -0,0 +1,28 @@
+// +build windows
+
+package directory
+
+import (
+	"os"
+	"path/filepath"
+)
+
+// Size walks a directory tree and returns its total size in bytes.
+func Size(dir string) (size int64, err error) {
+	err = filepath.Walk(dir, func(d string, fileInfo os.FileInfo, e error) error {
+		// Ignore directory sizes
+		if fileInfo == nil {
+			return nil
+		}
+
+		s := fileInfo.Size()
+		if fileInfo.IsDir() || s == 0 {
+			return nil
+		}
+
+		size += s
+
+		return nil
+	})
+	return
+}