Luarocks List.lua from Lua script

[Russell Haley <russ.haley@...>]

Hi there,

I don't know if this exercise was academic or not, but I couldn't
figure out how to call "luarocks list" from within lua other than the
command line tool. I modified list.lua to also export a list(...)
command that returns table,table,table string: results, trees, flags,
version.

If anyone else would find that useful I'll fork and create a pull
request (and do some more testing!).

diff
http://pastebin.com/jxD2zSDG

test jig
http://pastebin.com/kgVBZRLs

Cheers,

Russ