be able to contructor a serializer with output configuration

yaserde/src/ser/mod.rs

@@ -12,6 +12,13 @@ pub fn to_string<T: YaSerialize>(model: &T) -> Result<String, String> {
   Ok(String::from(data))
 }
 
+pub fn to_string_with_config<T: YaSerialize>(model: &T, config: &Config) -> Result<String, String> {
+  let buf = Cursor::new(Vec::new());
+  let cursor = serialize_with_writer(model, buf)?;
+  let data = str::from_utf8(cursor.get_ref()).expect("Found invalid UTF-8");
+  Ok(String::from(data))
+}
+
 pub fn serialize_with_writer<W: Write, T: YaSerialize>(model: &T, writer: W) -> Result<W, String> {
   let mut serializer = Serializer::new_from_writer(writer);
   match model.serialize(&mut serializer) {
@@ -93,3 +100,9 @@ impl<'de, W: Write> Serializer<W> {
     self.writer.write(event)
   }
 }
+
+pub struct Config {
+  perform_indent: bool,
+  write_document_declaration: bool,
+  indent_string: Option<String>
+}