Rainbows! 4.4.2 - EventMachine async.callback fix

Rainbows! is an HTTP server for sleepy Rack applications. It is based
on
Unicorn, but designed to handle applications that expect long
request/response times and/or slow clients.

Changes:

One bugfix allows stream(:keep_open) in Sinatra to work
properly. No changes for non-EM users.

Thanks to W. Andrew Loe III for the informative bug report
and reproducible test case.

ref:
http://mid.gmane.org/[email protected]