Add handler decorator to allow a existing class to be decorated

This also changes the behaviour of adding signal and method handlers to DbusHandler classes
Previously only methods on the current class where considered. Now also methods on the superclass are considered
Add travis-ci configuration
Add build status to readme
Add requirements file for travis to use
Rename README so it is clear it is in Markdown
Ofcourse it is in rst format and not markdown
Wrong filename for requirements.txt
Build c module before test
Fix last bug in python 3 where byte arrays where handled the wrong way
Merge branch 'master' into p3k