The html
data attribute does exactly what it says it does in the docs. Try this little example, no JavaScript necessary (broken into lines for clarification):
<span rel="tooltip"
data-toggle="tooltip"
data-html="true"
data-title="<table><tr><td style='color:red;'>complex</td><td>HTML</td></tr></table>"
>
hover over me to see HTML
</span>
JSFiddle demos: