Also wrap Errno::ETIMEDOUT.

Got it today in :
  Operation timed out
  whois (2.7.0) lib/whois/server/adapters/base.rb:195:in `read'
All Errno::* exceptions inherits from SystemCallError, so use that.
SystemCallError needs an argument, try the real exceptions.

SystemCallError is a special kind of exception, you should not call it
by yourself :

    1.9.3 (main):0 > SystemCallError.new(1)
    => #<Errno::EPERM: Operation not permitted>
    1.9.3 (main):0 > SystemCallError.new("foo", 1)
    => #<Errno::EPERM: Operation not permitted - foo>
    1.9.3 (main):0 > SystemCallError.new("foo")
    => #<SystemCallError: unknown error - foo>
Add a missing require in socket_handler_spec.
Merge pull request #212 from Absolight/ETIMEDOUT

Also wrap Errno::ETIMEDOUT.