Update to Piggieback 0.1.2 and add support for cljs.repl compiler environments

I was getting NullPointerExceptions while trying to use cljs-noderepl with the latest ClojureScript. This would also happen with Piggieback/nREPL.

After updating to the latest Piggieback, I realised that the call to `node-setup` in `nrepl-env` was causing problems. It would give a NullPointerException while internally deref'ing the compiler var.

I've now wrapped the node-setup function to use the repl-env compiler environment or the default one. I also added the default compiler environment to the node repl-env.

With these changes, the REPL can now be launched using the 3 prescribed methods in the README, using the latest ClojureScript, Piggieback and Node.