user/jszakmeister: add Clojure insert mode binding to slurp and barf

This mostly matches what is done in Emacs's paredit mode.  The one
exception is that paredit for Vim doesn't reformat the block, but I may
add code to do that down the road.  This is still experimental.
user/jszakmeister: Update to 82406ff of paredit

This one contains my bug fix for v).