updated ffi-rzmq dependency and relaxed requirement
updated version
tighten ffi-rzmq requirements again
Actually we want ffi-rzmq ~> 1.0.1
Merge branch 'skaes-ffi-rzmq-1.0' (closes #23)
Update ffi-rzmq to ~> 2.0.1 to allow zeromq 4.x

zeromq 4 is the latest stable and ffi-rzmq 1.0.1 only supports up to the 3.x
series.
Merge pull request #25 from zimbatm/ffi-rzmq-update

Update ffi-rzmq to ~> 2.0.1 to allow zeromq 4.x
changed logic which defines NOBLOCK
updated version to 0.5.0