Extending default editor

Hi, i'm trying to extend the default editor so I can add some other format options. Currently you only have paragraph (normal text), headings, quote and code.

I'd like to add blockquote and some classes into that. For example, let's say i'd like to add this class when I choose "Lead text" from the format options:

<p class="lead">Text</p>

Where can I configure that? I really like your editor and would like to avoid changing it if I don't need to.