DOC: some rewording of highlights
@jreback I proofread the highlights and made some edits (but language is always a bit subjective). Comments?

trivial change. lgtm. merge away (I have a small doc fix w.r.t. the float indexers section but orthogonal)
 I fixed the float indexers code block issue already on master, a colon was missing
 oh ok, then i'll rebase on top
