Add support for State.send_reply which states can return false from in order to not reply at all.
Add test for handling of send_reply in interaction machine.
Remove ancient test blocks that should be implemented (but not in this file).
Merge branch 'feature/issue-33-allow-states-to-not-reply' into develop
Merge branch 'develop' into release/0.1.x
Version 0.1.20.