Created Poll class.
Poll packages sockets into poll items.
Packaged PollItem array into C pointers.
Moved timeout into an accessor.
Had to memcpy PollItem.
Polling brings result back into Ruby and calls block.
Refactored Poll to eliminate the double memcpy.
Poll yields the ZMQ::Socket object and revent flags.
Refactored Poll's hash of triggered items.
Implemented Poll#run.
Implemented Poll socket args tests.
Added tests for timeout options.
Added nonblocking convenience methods.
Implemented Poll return value tests.
Removed testing of event types; it's done in other tests.
'timeout' was already required in spec_helper
Add 1-second timeout to other tests