hasAnswer() or understood() method

[tanftw]

Sometimes, we need to check if bot is has already understood some answer, so it won't override old answer, we'll create hasAnswer() or understood() method:

$bot->hasAnswer('foo');

or

$bot->understand('foo');

For example:

if ( ! $bot->understand('hi'))
{
    $bot->answer('hi', 'Hi [first_name]!');
}

// Which equal to

if ($bot->doesntUnderstand('hi'))
{
    $bot->answer('hi', 'Hi [first_name]!');
}