tests: create the in-memory database once in setup_module() Also mock the correct method, close() instead of disconnect().

viewer: get_or_404() to raise 404 (instead of 500) when model doesn't exist

tests: test index page and a non-existent page that gives 404

tests: mock database to be an in-memory db for tests

tests: add test_models with some Check.get_duration() checks

viewer: don't show "0 sec" in get_duration() if check took exactly X minute(s)

viewer: don't show last check date if there are no checks

checker: use default directory for mkstemp (influenced by TMPDIR, TEMP or TMP)

viewer: don't wrap text in columns with status badges

docs: add license