Rename API method 'redraw' more specific 'reflow'

The 'edited' hook was originally named 'redraw', and I mistakenly
renamed it in #241 thinking they should mean the same thing, but undid
that in the parent commit.

Just did:

    sed -i '' s/redraw/reflow/g $(git grep -l redraw)

and rewrote the README entry.

Recommend --word-diff-regex='\w+|\S' to view diff.