geom_text(aes(tooltip)) does not work

[tdhock]

because tooltips are currently implemented by adding <title> elements inside the svg element, but the JS .text method is removing the <title> element and replacing with the aes(label) value.
we could conceivably get it to work by making html like label text<title>tooltip text</title>
but even better is if we could implement a new tooltip library with more rapid/obvious tooltips that show up.