Features added:
1. *e returns the most recently thrown error in the REPL.
2. If multiple forms are submitted at the REPL, then forms are evaluated in order until
   an error occurs. If an error occurs, the error is printed. Otherwise the value of the
   last form is printed and assigned to *1.
3. Line numbers are shown for all printed errors.
use cljs.core/*e instead of clojure.core/*e
Merge pull request #28 from arthuredelstein/web-edit

REPL behavioral features (*e, more err line numbers)