Merge tag 'v2.3' into develop

OireMail, version 2.3: better HTML mark-up, readme in Textile now, and much more (see the changelog)
Merge tag 'remove-travis-for-now' into develop

Removing travis build for now. Should make it as a separate feature, maybe adding composer.json and other building files.
Adding Composer and Travis support
Bumping version
Merge branch 'release/v2.3.1'