missing i18n, html-safety audit

tweak Tooltip so that it will escape content unless given a SafeString

test plan:
analytics tooltips should work and look correct

Change-Id: Idbd637398e172d2f447350e34d3edb02414e669d
Reviewed-on: https://gerrit.instructure.com/46231
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Michael Ziwisky <mziwisky@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Jon Jensen <jon@instructure.com>