Changed size restrictions and resizing behaviour.
* Added a view_type that can display a week, 2 weeks or a month.
* Rename self.step to self.day_width
Commented functions.
Always start showing the current week/month.
* Hard coded tasks start and end dates are now relative to 'today'.
* Added seed to random methods to always generate same colors/dates.
Interface change: added buttons to switch between views.
* Added 3 buttons to show different views: week, 2weeks or month.
* Added 'today' button to go to current week/month.