npm spec eats translation errors

[mikesamuel]

gulp spec and gulp spec.watch use npmjs.com/package/bikeshed-js which is nice since it falls back to the bikeshed webservice if you haven't installed bikeshed locally, but which eats errors.

Right now, gulp spec

• dumps error output to the HTML target file instead of the console
• silently eats non-zero response codes
• it's not obvious how to specify strict flags.

I ran

$ bikeshed --die-on link-error --print console spec spec/index.bs dist/spec/index.html

during local development .

Maybe rewrite the gulp file to just call out to bikeshed when it's available on PATH.

The bikeshed executable has a watch command so setting up the watcher to be equivalent shouldn't be super hard.