Update ruby-eventmachine to 1.2.0.

## 1.2.0 (March 15, 2016)
* Integrate work from the EventMachine-LE 1.1.x versions [#570]
* Add start_tls options :ecdh_curve, :dhparam, :fail_if_no_peer_cert [#195, #275, #399, #665]
* Add start_tls option :ssl_version for choosing SSL/TLS versions and ciphers [#359, #348, #603, #654]
* Add start_tls option :sni_hostname to be passed to TLS params [#593]
* Add method EM::Channel#num_subscribers to get the number of subscribers to a channel [#640]
* Add support for proc-sources in EM::Iterator [#639]
* Factor out method cleanup_machine to cleanup code from EM.run [#650]
* Replace Exception class with StandardError [#637]
* Close socket on close_connection even after close_connection_after_writing [#694]
* Allow reusing of datagram socket/setting bind device [#662]
* Handle deferred exceptions in reactor thread [#486]
* Reimplement Queue to avoid shift/push performance problem [#311]
* Windows: Switch from gethostbyname to getaddrinfo, support IPv6 addresses [#303, #630]
* Windows: Use rake-compiler-dock to cross-compile gems [#627]
* Windows: Add AppVeyor configuration for Windows CI testing [#578]
* Windows: Bump rake-compiler to version 0.9.x [#542]
* Fix compilation on AIX (w/ XLC) [#693]
* Fix build on OpenBSD [#690]
* Fix OpenSSL compile issue on AIX 7.1 [#678]
* Fix EventMachine.fork_reactor keeps the threadpool of the original process [#425]
* Fix to prevent event machine from stopping when a raise is done in an unbind [#327]

(taca)