Include Cc and Bcc when sending MIME messages

It wasn't obvious enough that when sending MIME messages, all recipients need to be included in the 'to' parameter, otherwise those recipients will not receive the email.
fixed spelling error
Update user_manual.rst

Added a predefined template variable %recipient_email%
Merge pull request #35 from objectrocket/master

fixed spelling error
Merge pull request #39 from jesinwp/patch-1

Update user_manual.rst
Merge pull request #33 from RubenKruiswijk/patch-1

Include Cc and Bcc when sending MIME messages
Removal of Mailbox API references.
Merge pull request #40 from mailgun/MailboxEOL

Removal of Mailbox API references.
Merge pull request #1 from mailgun/master

Update fork from original