Properly handle read-write/read-only windows<->posix (fixes #236)

model/util.go

@@ -12,11 +12,13 @@ import (
 
 func Rename(from, to string) error {
 	if runtime.GOOS == "windows" {
+		os.Chmod(to, 0666) // Make sure the file is user writeable
 		err := os.Remove(to)
 		if err != nil && !os.IsNotExist(err) {
 			l.Warnln(err)
 		}
 	}
+	defer os.Remove(from) // Don't leave a dangling temp file in case of rename error
 	return os.Rename(from, to)
 }