text-formatter: do not quote 9

text_formatter.go

diff --git a/text_formatter.go b/text_formatter.go
index def60e9..2d884c0 100644
--- a/text_formatter.go
+++ b/text_formatter.go
@@ -110,7 +110,7 @@
 	for _, ch := range text {
 		if !((ch >= 'a' && ch <= 'z') ||
 			(ch >= 'A' && ch <= 'Z') ||
-			(ch >= '0' && ch < '9') ||
+			(ch >= '0' && ch <= '9') ||
 			ch == '-' || ch == '.') {
 			return false
 		}

text_formatter_test.go

diff --git a/text_formatter_test.go b/text_formatter_test.go
index f604f1b..396bc5f 100644
--- a/text_formatter_test.go
+++ b/text_formatter_test.go
@@ -25,6 +25,7 @@
 
 	checkQuoting(false, "abcd")
 	checkQuoting(false, "v1.0")
+	checkQuoting(false, "1234567890")
 	checkQuoting(true, "/foobar")
 	checkQuoting(true, "x y")
 	checkQuoting(true, "x,y")