v1.0.3

• new feature
  • support write 'null' with empty value in json
  • support custom codec
  • support use enum as map key
  • support customize xml vector label
  • encoder support SetMaxDecimalPlaces
  • json support NaN
  • xml support CDATA
  • json support encode vector in single line
• bug fix
  • fix xml encoder bug when vector size zero
  • fix encoder bug when omit empty