Refactor `clear' and `manual_clear'

See https://github.com/esl/wombat/issues/784

*TODO* update doc and version
Bump version to 0.3.0
update doc
Merge pull request #35 from horvand/refactor-clear-message

Refactor clear message
Remove empty trailing line

The real reason of the commit is that we need to push a commit into GitHub in
order to trigger Travis CI.
Improve Readme, add Travis badge.

* Also build with 17.1
Adding eunit to apps for Dialyzer

* Make Dialyzer understand eunit:test/1
Adding purge target to Makefile
Merge pull request #36 from lastres/improve-readme

Improve Readme, add Travis badge.
Merge pull request #37 from sata/add-eunit

Add eunit to apps in Dialyzer build_plt and a new purge target