Third-party code credits

In vagrant/tournament_extra_credit/tournament.sql:

• The sql function check_match_tournament_membership() and related trigger were created using the code in the following document as a starting point: http://www.postgresql.org/docs/9.0/static/plpgsql-trigger.html

In vagrant/tournament_extra_credit/tournament_test.py

• Many of the additional tests are based on tests in the original file provided.
  • testStandingsBeforeMatchesByTournament() is based on testStandingsBeforeMatches()
  • testReportMatchesByTournament() is based on testReportMatches().
  • testPlayerStandings() is based on testReportMatches().
  • testPairingByTournament() is based on testPairings().