Sylvia/docs/1162

@talbs Here's the PR for the calculator tooltip. Thanks again and in advance for the help.

@lamagnifica @mhoeber @catong Brian and I are going to discuss whether we'll be resizing the tooltip and/or changing the tooltip's behavior or moving this info into a more suitable UI element. If you have any thoughts about the content or the way it's organized, feel free to comment here or in the JIRA ticket.

JIRA link: https://openedx.atlassian.net/browse/DOC-1162
These elements should be contained within a table header (``<thead>``) and marked up as ``<th>``.