Fixed inheritance problem in testExtractsContent...

This test was not inheriting from django.TestCase, so the
tests were not executing with 'python manage.py test'.
Added header scraping functionality.

PageScraper can now scrape:

- race name
- event name
- race location
- race date
- race director

This is done using regular expression matches which correspond to
'standardly' formatted result files.  These methods also have the ability
fallback to a less agressive match of the content.
Fixed bug #10, loss of pre tags during filtering.

The <pre> tags are now included in the race result lines returned
after filtering.  The pre tags are not always on their own line, and
sometimes these lines also contain race related information.