Replace "~some_id~" placeholder notation with "<some_id>", enclose headers in `backticks`
Replace "~some_id~" placeholder notation with "<some_id>", enclose headers in `backticks`

GitHub renders ~some_id~ as <del>deleted text</del> which looks ugly.

berkmancenter/mediacloud,berkmancenter/mediacloud,berkmancenter/mediacloud,berkmancenter/mediacloud,berkmancenter/mediacloud