Tables

Hi, I implemented simple tables for the maruku dialect (more or less following [PHP Markdown Extra][]'s implementation), as I needed them for a project of mine where I use this lib. Tests are still missing though...

[PHP Markdown Extra]: http://michelf.ca/projects/php-markdown/extra/

A difference is that  this implementation does not force cells in a row to be created up to the maximum width of the table... don't know yet if it's a big deal.

There are also some other minor changes that ended up in the code: the correction of a leaking global variable, the parameterisation of escaped characters per dialect (markdown extra apparently needs escaping for : and |),  and a break statetement to exit a loop cheking for an empty dictionary.

edit: corrected typo