Dkim signing for outgoing emails

[seriyps]

Actualy, added support for DKIM signing in mimemail module.

Unfortunately, this patch also include not-yet-merged part from issue #36 (permissive headers parser), but it may be merged separately, from my master branch.

Tests included, as well as documentation (in README).

I have this code in production server for about 2 days (2 days with simple canonicalization and ~2 hrs with just implemented relaxed canonicalization algorithms) with 0 problems: google and other mail services accept this signature:

Authentication-Results: mx.google.com;
       spf=pass (google.com: domain of from@dropmail.me designates 178.132.203.233 as permitted sender) smtp.mail=from@dropmail.me;
       dkim=pass header.i=@dropmail.me
DKIM-Signature: s=dkim-1;
     h=from:to:subject:date;
     d=dropmail.me;
     c=relaxed/simple;
     bh=MT4vVVSfMe5EiYhAAMxVct2CWoLsljxiRtRzKYgC4tk=;
     a=rsa-sha256;
     v=1;
     b=Nz7w+VT0aRWhKp7vYWUevnc6onP94RKq0bYR6iFl3kA2bsA3sb5e08ZCF7rL0nFHXJWyKx93mczw2t19P/gQV+QRtFjZK/RNBN408hqFN9AQ3G1kIAF7MGS4c/t+uNPWxTyoB9kihlbrcgTZMYmKZ6Qbm/cbUWS8A/N/ETIAEik=

P.S.: this DKIM stuff may be implemented in separate module, because it uses only few functions from mimemail, so, this is a subject for discussion.

[seriyps]

So, 2 weeks in production - DKIM works with no issues.
What can I do to make this merged?

[Vagabond]

I'd like to see this go in, although I'm short on review time right now, and there's a lot to digest here.

[mworrell]

Looks like quite some commits are actually coming from the master. The DKIM commits are not so many.

@seriyps any commits we need to look at specifically?

[seriyps]

@mworrell yeah, as I noted, some of commits in this branch are not relevant to DKIM, they appears in this pull-request, because I've implemented DKIM on top of my fork, but not directly from upstream. But I don't know how to separate them from this branch. I think, if I make another pull-request of my master branch, which include only not-yet-merged improvements of MIME-parser, DKIM patch will become much smaller.
Sorry for confusing you, my GIT skills are not so well.

[seriyps]

replaced by #57