reflect Bootstrap's org change

Bootstrap is no longer formally organizationally associated with Twitter, so it should be referred to simply as "Bootstrap" rather than "Twitter Bootstrap"; see https://github.com/twbs/bootstrap/blob/4120aadd68ddd15d2b8f0cddc9c72118caec9923/docs/about.html#L36

Also fixes the spelling of Font Awesome (two words, not one).