Add operatorfunc function, new mapping, and cleanup README

This lets us do things like `,<ip` to export a paragraph.  I've really missed having this, and now that I've tried it out, it's pretty slick.

Also I fixed up the `README`, including the rather glaring omission of our syncopate-specific configuration options.
As it happens, I was also unhappy with my wording here.  I prefer yours.  I'll fixup and merge.  Thanks!