New autocompleters: aggregate and path.

Example:

    use Hoa\Console\Readline;
    use Hoa\Console\Readline\Autocompleter;
    use Hoa\File;

    $readline = new Readline();
    $readline->setAutocompleter(
        new Autocompleter\Aggregate([
            new Autocompleter\Path(
                Autocompleter\Path::PWD,
                function ( $path ) {

                    $finder = new File\Finder();
                    $finder->in($path)
                           ->files()
                           ->directories()
                           ->maxDepth(1)
                           ->sortBySize();

                    return $finder;
                }
            ),
            new Autocompleter\Word(
                get_defined_functions()['internal']
            )
        ])
    );

    do {

        $rl = $readline->readLine('> ');
        echo '< ', $rl, "\n";

    } while(true);

Thanks @jubianchi for the review!