Don't print escaped strings for the default value of string flags with a default is set.

Signed-off-by: Daniel Nephin <dnephin@gmail.com>

flag.go

diff --git a/flag.go b/flag.go
index d9aee57..fa81564 100644
--- a/flag.go
+++ b/flag.go
@@ -534,7 +534,7 @@
 		line += usage
 		if !flag.defaultIsZeroValue() {
 			if flag.Value.Type() == "string" {
-				line += fmt.Sprintf(" (default %q)", flag.DefValue)
+				line += fmt.Sprintf(" (default \"%s\")", flag.DefValue)
 			} else {
 				line += fmt.Sprintf(" (default %s)", flag.DefValue)
 			}