Merge pull request #68 from sorairolake/fix-string-example

Fix string generation example in README

README.md

@@ -55,6 +55,7 @@ use qrcode::QrCode;
 fn main() {
     let code = QrCode::new(b"Hello").unwrap();
     let string = code.render::<char>()
+        .dark_color('#')
         .quiet_zone(false)
         .module_dimensions(2, 1)
         .build();