add get_file_descriptor
Pause receive_data on-demand

When receiving large amounts of incoming data, we loop over recv() up to
10 times to drain the inbound buffers. This meant calling #pause from #receive_data
would previously not take effect until the next reactor tick.
Merge pull request #464 from eventmachine/pause-during-receive_data

Immediate pause from receive_data
update changelog
Add EventMachine.attach_server & EventMachine.attach_socket_server.
Simplify the attach_server stuff to 1 method, hold a reference to the socket.

Otherwise the FD could be closed by a GC.
Merge pull request #465 from benburkert/attach_server

Add EventMachine.attach_server & EventMachine.attach_socket_server
Return the signature ID from EventMachine.attach_server.
Merge pull request #466 from benburkert/attach_server_signature

Return the signature ID from EventMachine.attach_server.
Merge pull request #467 from brianmario/add-get-fd

Add get_file_descriptor which returns the FD number of a signature
Added concurrency validation
Added unit tests for EM::Iterator
Merge pull request #468 from morandanieli/iterator_fixes

Added concurrency validation to EM::Iterator
Add Code Climate badge to repo
Merge pull request #470 from mrb/patch-1

Add Code Climate badge to repo