Update to work with netcoreapp1.0 and .NET Core 1.0.1

[cocowalla]

I guess this is already on your radar after your recent merge in SyslogNet.Client-dnx, but it would be great to have this project also updated to be compatible with .NET Core, and then new NuGet packages published for both projects.

BTW, it looks like @realityenigma already worked on this in a fork, but I can't see a reference to it in this repo.

[realityenigma]

I handled my work at https://git.integrisok.com/INTEGRIS/SyslogNet.Client-dnx if you are interested.