Support for HTML class'es on DataFrame.to_html().
I really like to use sorttable.js and dragtable.js.
I need to be able to customize the HTML classes.
I also added a default class, so that people can use css on all Pandas generated tables by default.
Default class is "dataframe"

I've also added support for formatting the index using the optional formatters argument.
 I included to_latex() support. 
I've really, _really_ basic for now, but it works.
We can refine it later if some people want options. I pass the kw options through, so that'll be easy.
