Resize thread pool and set TcpStream timeout

[sigaloid]

This fixes the trivial attack of slowloris'ing 10 threads and holding them open forever.

1. the thread count is dynamic (up to 400 threads in my example but that's not a hard limit and depends on use case; it also rescales back down based on demand)
2. the stream is killed after one second (also depends on use case)

Basically just proposing an idea that the thread pool be resized. :)