Fixed some unintuitive behaviour in `Transformer.{cut,copy}`. The old behaviour was to copy all selected events in the stream before passing to the next transform. The new behaviour is to copy only a single contiguous block before yielding to the next trasnform. The previous behaviour can be preserved with the following construct: `...copy(buffer, accumulate=True).buffer()...`

Sample application that demonstrates the use of Genshi templates in web.py
(http://webpy.org/).

Try introducing errors (not just XML well-formedness errors, those are boring)
in the template, and you'll see a nice error screen with pretty good
information about the exact error.