Client#reset uses the presence of @buffer to detect if there is a
partial next request available. Thusly we have to be sure to nil it out
after we use @buffer otherwise we'll accidentally replay the request
over and over again.
Previously, the app thread would be in charge of reading the request
directly from the client. This resulted in a set of slow clients being
able to completely starve the app thread pool and prevent any further
connections from being handled.
This new organization uses a seperate reactor thread that is in charge
of responding when a client has more data, buffering the data and
attempting to parse the data. When the data represents a fully realized
request, only then is it handed to the app thread pool. This means we
trust apps to not starve the pool, but don't trust clients.
