preview3 -> preview4 repl improvements

gistfile1.txt

REPL-y/jline2 features:
- blink-matching-parens

REPL-y/jline2/nREPL bugs:
- fix garbage output when editing multiple lines
- allow printing after a value is returned
- add cdoc alias
- fix clojuredocs command in a new project
- avoid warnings and errors for jlinerc and inputrc
- avoid nesting agents (Chas Emerick)
    
Lein features:
- Allow trampolining the repl task