Biscuit WIP

There's a lot of changes here, primary changes:

* Refinement and stabilization of HTTP server.
* Change HTTP server to execute gulp build / capture errors.   This is done by passing the --baking flag to the gulp build.  Gulp then reports errors to `stderr` as `json` representations of `biscuit-utils.GulpTaskError` which are easily parsed and understood by the biscuit http server.

@markschaake It might be hard to review this without seeing the code but feel free to take a look before merging!