Eliminate need for explicit configuration of request/response buffer sizes

[cemerick]

Addressing aantron/dream#214 required modifying dream to accept an Httpaf.Config.t so that a much higher read_buffer_size could be specified to avoid parsing problems when consuming/receiving larger websocket messages.

While provisioning larger buffers does guard against failures involving messages smaller than that buffer size, it's clearly (a) a waste of resources for the vast majority of (usually small) ws messages, and (b) does nothing to protect against failures with the rare message that does exceed even the over-provisioned buffer size.

In private communications with @anmonteiro discussing this problem in general, he indicated:

that does indicate a bug in the parser for websocketaf IMO
we should probably commit the parser more often

Opening an issue here now as a bookmark for future improvements; looking around at a couple of other websocket implementations (e.g. https://github.com/websockets/ws), none seem to have any explicit buffer configuration options, choosing instead to dynamically allocate to accommodate arbitrary message sizes. This is presumably the direction websocketaf should move in.

[jdf-id-au]

Netty has maxContentLength and maxFrameSize and some corresponding exceptions, (the first of which was possibly misleadingly used?)

[cemerick]

An update: a recent commit (44c5429) was AFAIK intended to address this, but does not. The same behaviour noted @ aantron/dream#214 remains, as of aantron/dream@a39c938

[anmonteiro]

Buffer sizes are quite unrelated to garbled data. The design of this library follows http/af and h2 where we perform unbuffered parsing with angstrom.

I believe I've addressed the source of garbled data, and I believe this issue can be solved separately by committing the parser more often (and therefore freeing space in the buffer).

[anmonteiro]

we fixed the garbled data issue in #68. I don't plan on removing the need for the low-level configuration of buffer sizes, but will reopen this issue if I change my mind.