specify node/browserify version to use when bundling

We have to globally upgrade node and browserify right now which on the one hand is nice because we get new versions, but is bad from an API standpoint because the same GET request to wzrd.in one day might return different results the next day.

It would be cool if we strived towards reproducibility by default in the HTTP API, so you could specify the node + browserify versions in the GET requests to build a module in a specific environment

Maybe combined with https://github.com/jfhbrook/wzrd.in/issues/117 this wouldn't be too bad to implement

Start by reviewing the HTTP API and issue #117 to understand the existing bundling flow and how version selection could be exposed. Done means clients can request specific Node and Browserify versions and repeated requests with those versions produce reproducible results.

Written by the indexing model from the issue text.