An simple nrpl for nim

[kaushalmodi]

@slangmgh I am unable to run `nims` on Linux. I just did git pull and rebuilt 
with `nim c -d:release -d:nimcore nims.nim`, but running `nims` gives me this:
    
    
    > nims
    1>>> NimVersion
    2>>> echo "A"
    3>>> exit
    4>>> quit
    5>>> Error: EOF reached
    1>>> ^CCTRL-C pressed, quit.
    
    
    Run

I don't know if you have subscribed to Issues on your repo, but I have already 
created an issue there: <https://github.com/slangmgh/nims/issues/4> .