choose style of table with one option instead of one for each table format 

There are a lot of great different table formats available for hirb now: 
"normal", "markdown", "vertical", "tab" and "unicode"

For each format a separate symbol in the option hash exists, but you can
display data only in one format at any time. Why not replace all
separate options with one :style option, which can be extended if a new
table format becomes available; with no need to clutter the option hash
with new symbols for the :next_fancy_table_format.

Please be aware that the patch for moca + test/unit was included by
accident.

Cheers,
MaxMeyer