Remove rbczmq from dependency
Remove rbczmq from dependency

I don't know what is the best solution about add_runtime_dependency.
If this line is not removed Windows users will very confused, but if not
users will wonder how to solve LoadError 'ffi-rzmq' or 'rbczmq'.

SciRuby/iruby,SciRuby/iruby,zalt50/iruby,SciRuby/iruby,zalt50/iruby,zalt50/iruby,SciRuby/iruby,zalt50/iruby