Formatter + getting rid of these annoying warnings on 1.9

Hi Sindre,

can you please check my two commits? I think the commit messages are self-explanatory. I think you'll be glad, I moved all the formatting methods into a DefaultFormatter and now it's easy to create another fromatters, let's say HTMLFormatter, XMLFormatter etc. I'm about to write a YAMLFormatter which I need for my project.

Cheers,

Jakub