Enhance Repl

https://github.com/meric/l2l/pull/47#issuecomment-246272371

The repl supports partial input, but it bases it on the error message string to determine partial input: if(src_or_err:find("no bytes$")) This could be made more explicit somehow.

Printing of regular tables is still Lua's stupid opaque method: table: 0x10c8700 so we should add some pretty-printing at some point.