Puma::IOBuffer is a very simple memory buffer that allows for fast
append without additional object overhead.
Additionally, turns out that IO#write on 1.9.3 is extremely
non-performant because it allows a Hash object on every invocation.
Avoid calling IO#write in a loop on 1.9.3! Use IO#syswrite if you can
(for instance when you don't care about the encoding of the output
(sockets)).
