Changed example for context manager from a sockets to copying a file because as of Python 3 sockets already have a context manager.
Ignored LibreOffice locks and files generated by exmaple programs.
Fixed example usage of NaiveCopyTask (which wasn't called at all).
Cleaned up redundant attributes.
Added slides for talk at EuroPython 2014. The video is available at <http://www.youtube.com/watch?v=kT34QMil-FQ>.