Add EventMachine::attach_server

EventMachine::attach_Server is for attaching an arbitrary server IO
object or file descriptor to the event loop.

Tries to fix #93.

Signed-off-by: Ramon Marco L. Navarro <ramonmaruko@gmail.com>
allow jruby users to opt out of the Java EventMachine reactor
Merge remote-tracking branch 'socket-patch/attach_server'
Merge branch 'master' of https://github.com/scoreloop/eventmachine