Log Message:
Update ruby-mail to 2.6.5.

== Version 2.6.5 - 2017-04-26 Jeremy Daer <jeremydaer@gmail.com>

Features:
* #1053 - Ruby 2.4.0 compatibility. Fixnum+Bignum unified as Integer. (peterkovacs)

Bugs:
* #605 - Fix Mail::Address#name for nil addresses (peterkovacs)
* #1003 - Fix decoding some b encoded headers on specific rubies that don't \ 
account for lack of base64 padding (kjg)
* #1023 - Fix double-quoting in display names. (garethrees)