added an extension to IWebHost

[Trapov]

ended up doing this.
Issue -> #57

[dasMulli]

I don't really like the idea of adding a dependency on either .Hosting or .Hosting.Abstractions to the main package since it adds quite a lot of dlls to non-asp.net core projects.
Additionally, there will likely be updates to the hosting / abstractions that don't need to cause updates to the main service functionality. E.g. there will be a new hosting model in 2.1 (IHost vs IWebHost) and I still want the main package to work in both 2.0 and 2.1.

What do you think about making this its own nuget package? (I could do so after merging).

[Trapov]

@dasMulli ya, i was thinking the same actually. but this feature doesn't really require the whole project, so it feels kinda bloated with not needed dependencies. It would be great if you could breake your project into different layers and then it would be really small and lightweight :)

but yes, i will update my PR and make this extension as a different project for now.

[Trapov]

@dasMulli wait i haven't updated my PR still, i thought you wanted it as a separate project.

[dasMulli]

I'm on that already 😉

[Trapov]

@dasMulli oh, ok, great then. feels like i dropped something that i had to do on you tho :)

[dasMulli]

see #59