Coverlet.Collector.nuspec puts files in the wrong folder

[AArnott]

The checked in Coverlet.Collector.nuspec file is missing this tag:

    <developmentDependency>true</developmentDependency>

which I'm guessing should be there since in fact it is present in the .csproj file, but not in the checked in nuspec file.

Also: all the files included in the package are placed under the build\netcoreapp2.0 folder, which will make the NuGet package only able to install into other .NET Core 2.0+ projects. But since this is a build authoring package, it probably can (and probably should?) apply to all kinds of projects. So the folder used should be build\netstandard1.0.

[AArnott]

I'm preparing a fix for these issues, which also eliminates the checked in nuspec file so that you don't have two files to maintain -- just the csproj.