Add doc to "C-1" and args to "C-2"

* lispy-inline.el (lispy-arglist-inline): new command
  (lispy-describe-inline): new command
  (lispy--arglist): new function
  (lispy--pad-string): new function
  (lispy--show): new function
  (lispy-face-hint): new face
  (lispy-overlay): new var
  (lispy-hint-pos): new var