De-dup.

Conflicts:
	test/postal/test/message.clj
Drop drop-keys in favour of dissoc.
Remove drop-keys function.
Add contributors.
Generate contributors from git log.

git log --pretty=format:"%an" | sort -u
Apply charset to subject.

Closes #36.
Add send-message test for two-arg arity
Prefer real connection arg over metadata in docs

Closes #42
Typo
Bump commons-codec version to 1.9.
Add sendmail parameter to sendmail-send

Fixes #34
Add 1.11.1 change note
Release v1.11.2