proposal: use server-buffer to serve GTFS-RT data

[derhuerst]

During the development of hafas-gtfs-rt-feed (sort of the German equivalent of this project), I also wrote serve-buffer:

Serve a Buffer via HTTP, with Range, conditional GET and GZip/Brotli compression support.

There is a surprising number of difficult-to-understand corner cases in the HTTP RFCs. I tried my best here, so that others don't have to write quick-and-dirty (which in the HTTP realm usually means slightly wrong) implementations. This library supports the following request headers:

• Accept-Encoding
• Range & If-Range
• If-None-Match/If-Match & If-Modified-Since/If-Unmodified-Since

This project could use server-buffer to enable client-side caching for the GTFS-RT feed.

hafas-gtfs-rt-feed uses it like this: https://github.com/derhuerst/hafas-gtfs-rt-feed/blob/b2afbf78a9697cceddd97330e663ca8bbb00eae9/lib/serve.js#L120-L143