Fix cases where line entered is whitespace
Fix cases where line entered is whitespace

- Don't add to history
- Print a newline like Clojure REPL does

odekopoon/planck,mkremins/planck,odekopoon/planck,crisptrutski/planck,odekopoon/planck,terhechte/planck,vijaykiran/planck,terhechte/planck,crisptrutski/planck,jobez/planck,jobez/planck,vijaykiran/planck,jobez/planck,vijaykiran/planck,mkremins/planck