[TextIncrement] Used autoload-dev
[TextIncrement] Added incrementations

Now it's possible to use the following methods on Text:

    $text->incrementCurrentLineNumber(42);
    $text->decrementCurrentLineNumber(23);

This is to avoid boilerplate code like:

    $currentLineNumber = $text->getCurrentLineNumber();
    $newCurrentLineNumber = $currentLineNumber + 42;
    $text->setCurrentLineNumber($newCurrentLineNumber);
[TextIncrement] Renamed $lines to $number

Took @pyrech feedback into account
Merge pull request #95 from gnugat/text-increment

Text increment