Allow standalone visualizer to take logfile path as CLI

[wschella]

relevant folder.

Possible way to do this somewhat nicely:

• add a simple little Express.js server in the bin folder (instead of relying on webpack-dev-server to serve the html and js)
• spawn this server when webpack has compiled, and let it take CLI args
• set some server state
• let the frontend depend on this server state

It might also be a lot cleaner to just create new visualizer-bin package for this.