Jormungandr: change date parse library

datetime parse date seems broken, '155' with format '%H%M%S' is not
rejected but parsed as 1h, 5mn, 5s...

so use use for the input date parse dateutil even if the 'guess'
mechanism seems a bit dangerous
Jormungandr: change parser of from_datetime of Schedules
Merge pull request #9 from l-vincent-l/change_route_schedule_datetime

Jormungandr: change parser of from_datetime of Schedules
Merge pull request #573 from antoine-de/change_journey_date_parse

Jormungandr: change date parse library