Merge pull request zeromq#587 from somdoron/master

Fix NetMQ not working Linux with dotnet core

Merge pull request zeromq#585 from somdoron/master

Upgrade to latest AsyncIO

Merge pull request zeromq#584 from somdoron/master

add support for Xamarin ios and android

Merge pull request zeromq#583 from masaeedu/relaxnetstandard

Relax netstandard platform requirement

Merge pull request zeromq#582 from somdoron/master

script to patch project.json file on CI

Update README.md