[minor] Better error reporting for modules not on npm
[api] Pull error stringification into separate library
[api] First crack at adding multibundles
[api] Add multibundle cache, expose on bundler
[api] multibundle caching and 302s
[doc] Documentation of new HTTP API
[api] Eschew multiple body format support in favor of all JSON all the time
[ux] Error message for non-specified deps
[public] Regenerated index.html