table height attribute warning is annoying

#449 made it optional to specify a table height attribute, which is great for those of us sizing the table with CSS. However, when I'm doing this intentionally, I don't want to see these warnings.

Can we add an option or setting that will silence these, probably on a per-table basis? That way I could provide an attribute like `requireHeight: false` to each table where I'm explicitly choosing not to set the height because I know CSS has it taken care of.

I think this should be pretty simple so I'm happy to put together a PR if that sounds appropriate :v: