Fix SkinnyMailer multibyte characters encoding failure

Fix SkinnyMailer multibyte characters encoding failure

1. (MessageBuilderFeature) Mailer does not encode email subject including multibyte characters.
2. (JavaMailOps) Sending email including multibyte characters in logging mode, the exception occurs: "java.nio.charset.UnmappableCharacterException: Input length = 2".

These issues occur on both Windows and MacOSX.