* Use namespace in configuration, as classes are now namespaced.
* Also use namespace in code for referenced to own sniffs.
* Do not use identifiers with further dots as this is no longer
supported, use ":" instead.
Relates: #82
* Allow executing tests for single sniff through phpunit '--filter'.
* Provide structure to add further tests for a single sniff.
* Make output more clear, which sniff was tested.
