fixing when requesting the same file
little factorization
add handling of new "espace pro" website for lcl
Do not crash if total_seconds() is not implemented

Which is the case with Python 2.6.
We could do the calculation ourselves, but this is not a very important
feature.
CleanText: Always return unicode
Fix filters doctests and add them to the usual test run
CleanText improvements

* \t is always in \s so no need to add it
* handle the non-breaking space thanks to the re.UNICODE flag
* add an option to keep (but normalize) newlines
* more tests
Add support for a default in Env
Help debug Filter errors