Reformat tag demonstration
Reformat tag demonstration

I did an experimental table based tag demonstration. In a way it binds the `README` to its GitHub rendering, but it is still quite readable in text form.

When I was done perhaps it looked like information that a reader can get just by looking at the code, but for someone new to BBCode it might be appreciated.

Without concluding whether it was a worthwhile improvement or not, I issue a pull request to leave the decision to others :-) .
Colbydude/BBCodeParser,Darklev/BBCodeParser