Update Serilog version requirement

[cocowalla]

Just upgradied to Serilog 3.0.0 and am getting:

[NU1608] Detected package version outside of dependency constraint: Destructurama.Attributed 3.0.0 requires Serilog (>= 2.8.0 && < 3.0.0) but version Serilog 3.0.0 was resolved

[cocowalla]

Ah, I see there's already a PR for this, just waiting on review (#66).

[SimonCropp]

you should be able to update to newest nuget now