Options added: font_size, read_only, init (callback), on_toggle (callback). Pubic method:isChecked, readOnly

*** Options Added ***
font_size: 10,              // Set the label font-size. Added by Daniel Lee
read_only: false,           // Set to readonly mode if true. Added by Daniel Lee
init: function() {},        // callback function for initialization Added by Daniel Lee
on_toggle: function() {}   // callback function for initialization Added by Daniel Lee

*** Public Methods Added ***
// Check the value of the current status
isChecked: function()

// Set/Unset read only
readOnly: function(value)