Reformulate structure

[DiegoLopesLima]

• [x] Remove the jQuery.fn.validateDestroy function and use a new sintaxe.
• [x] Add new methods (validate, options...).

Example:

// Validates a form.
$('form').validate('validate');

// Destroy all events and data of plugin.
$('form').validate('destroy');

// Sets the filter options to `*`.
$('form').validate('option', 'filter', '*');

// Gets the filter option.
$('form').validate('option', 'filter');

// Sets the conditional option.
$('form').validate('option', 'conditional', {
    property : 'value'
});