Rewrite API for simpler usage

Change-Id: Ia3662aa3faac44cdc0345179263ce65517ed50cb
Reviewed-on: https://pirx.atteo.com/gerrit/512
Tested-by: Sławek Piotrowski <sentinel@atteo.com>
Reviewed-by: Sławek Piotrowski <sentinel@atteo.com>
Update README

Change-Id: Ia35447d5882ad509038668d61d48224b7b052a1f
Reviewed-on: https://pirx.atteo.com/gerrit/524
Tested-by: Mr. Jenkins
Reviewed-by: Sławek Piotrowski <sentinel@atteo.com>
Change groupId

Change-Id: I9c881bb4f2f00418ec1264da5ea52307045631ca
Reviewed-on: https://pirx.atteo.com/gerrit/525
Tested-by: Mr. Jenkins
Reviewed-by: Sławek Piotrowski <sentinel@atteo.com>
Remove dependency on slf4j

Change-Id: I3c94329e09fa51a99f5c73a98a549f7c16fe18ad
Reviewed-on: https://pirx.atteo.com/gerrit/526
Tested-by: Mr. Jenkins
Reviewed-by: Sławek Piotrowski <sentinel@atteo.com>