[Fix #151] Display JVM and nREPL version information on start

After the changes we have:

```
REPL-y 0.3.2-SNAPSHOT, nREPL 0.2.3
Clojure 1.4.0
Java HotSpot(TM) 64-Bit Server VM 1.7.0_17-b02
        Exit: Control+D or (exit) or (quit)
    Commands: (user/help)
        Docs: (doc function-name-here)
              (find-doc "part-of-name-here")
Find by Name: (find-name "part-of-name-here")
      Source: (source function-name-here)
     Javadoc: (javadoc java-object-or-class-here)
    Examples from clojuredocs.org: [clojuredocs or cdoc]
              (user/clojuredocs name-here)
              (user/clojuredocs "ns-here" "name-here")
user=>
```