Allows pattern definition to work

[roni-estein]

Without this flag, json_encode will escape the slashes that the configuration. Consider the example from the iMask docs

var zipMask = IMask(element, {
  mask: '#00000',
  definitions: {
    // <any single char>: <same type as mask (RegExp, Function, etc.)>
    // defaults are '0', 'a', '*'
    '#': /[1-6]/
  }
});

[danharrin]

Thanks!