AsyncIO dependency

[splitice]

The AsyncIO dependency does not appear to be required to compile or use this library.

When removed, it is possible to compile for an Android/Mono target (yet to be tested).

[dalebrubaker]

@somdoron, do you have plans to release NetMQ4 out of beta anytime soon? lf so, I'll wait for that before looking at this.
Thank you.

[somdoron]

I'm not sure it is stabled yet.

Also I'm not really sure it can run without asyncio.

[splitice]

Its strange since trying to add using Nuget Zyre to an android (Xamarin) class library tells you its incompatible due to AsyncIO, whereas NetMQ is added fine.

I am not the one assessing this for compatibility on the platform, but I will be happy to let you know.