support xamarinmac20?

[tofutim]

Do you want to request a feature or report a bug?

• feature

What is the current behavior?
Cannot install nuget package to xamarinmac20 (Xamarin Mac Mobile Framework)

What is the expected behavior?
Can install and it works!

What is the motivation / use case for changing the behavior?
Support Xamarin.Mac which is parallel to Xamarin iOS and Android anyway

Which versions of Serilog, and which platform / OS are affected by this issue? Did this work in previous versions of Serilog?
Latest, Mac OS El Capitan+ (use Xamarin Studio to test)

Other information (e.g. stacktraces, related issues, suggestions how to fix)

[ghuntley]

Yup; good idea. Send in a PR please.

[ghuntley]

I'd still accept a PR that adds this. Send it in.

[chucker]

I took a stab at it with #17