Add netstandard2.0 as target framework

[mbp]

Problem compiles fine with netstandard2.0

This should fix #235

[CLAassistant]

All committers have signed the CLA.

[AppVeyorBot]

✅ Build ZendeskApi_v2 3.8.1-PullRequest334.4.build.247 completed (commit e996451a94 by @mbp)

[austingreendev]

This would be very helpful for some of the more modern core applications! Any chance of this getting merged?

[mozts2005]

I am willing to do this. But I want to make sure the test will still pass please change the test project to be .net core.

if they pass I will then merge this.

you should only have to change the project to be netcoreapp2.0

[AppVeyorBot]

✅ Build ZendeskApi_v2 3.8.1-PullRequest334.10.build.253 completed (commit 635926ba2b by @mozts2005)

[mbp]

Done, passes locally

[AppVeyorBot]

✅ Build ZendeskApi_v2 3.8.1-PullRequest334.11.build.253 completed (commit 1962229799 by @mbp)

[mozts2005]

Lovely thanks for this.

[freemstr]

Thank you
When do you think will 3.9.0 nuget package be available?
ZendeskApi_v2 is the last non-core reference I have and the above discussion is great news.