release v4.1.0

prepare for release

Merge branch 'master' into release/v4.0.0

release/v3.1.3 (fewlinesco#175)

This release contains:
- bump `gen_smtp` from 1.0.1 to 1.1.0

Merge branch 'develop' into release/v3.1.2

change version on mix

change version and changelog

Bump to v3.0.0

Release 2.1.0 (fewlinesco#132)

Update changelog and lib version