Added 3 new options: 'allSelected', 'minumimCountSelected' and 'countSelected'

'allSelected' can be used to overwrite the text shown when all the items are selected.
'minumimCountSelected' and 'countSelected' can be used to show a formatted text after X items where selected. For example: '4 of 10 selected' will be shown if 'minumimCountSelected' is set to 3 and 'countSelected' is set to '# of % selected'.
Also fixed a small typo 'isopen' changed to 'isOpen'