Compatibility:
* Restore LF=>CRLF conversions for properly encoded non-binary emails. (rubys)
* Gracefully parse certain invalid Content-Type headers. (rafbm)
* Support `x-uue` transfer encoding as uuencoding. (jkraemer)

Features:
* Expose Mail::Field#unparsed_value to read the raw field value, before parsing. (Tensho)

Performance:
* Speed up message encoding, especially with large attachments. (dalibor)

Bugs:
* Fix transfer encoding when message encoding is blank. (jakubonty, saks)
* Fix 7bit/base64 content transfer encoding mismatch. (ahorek)
* Fix UTF-8 attachment filename quoting. (ahorek)
* Fix `delete_all` using a readonly IMAP connection. (kimromi)