Add Leiningen 2.4.2

Current (2.4.3) leiningen has a problem running the repl outside of a project directory - https://github.com/technomancy/leiningen/issues/1625 -  so it's handy to be able to use versions to downgrade back to 2.4.2 until this is fixed. 

# known issues 

- 2.4.2 had a problem where it announced itself as 2.4.1 as documented here: https://github.com/technomancy/leiningen/issues/1605