EmbeddedFileProvider should not be compiled for netstandard1.0

[pranavkm]

The comment here says we should remove the TFM in 2.0: https://github.com/aspnet/FileSystem/blob/dev/src/Microsoft.Extensions.FileProviders.Embedded/EmbeddedFileProvider.cs#L57

[pranavkm]

cc @muratg - we should try and sort this for 2.0 if we plan on doing this.

[natemcmaster]

I tracked down the history of this comment. It was added here: #210 cc @BrennanConroy

@muratg any reason we should keep netstandard1.0?

[muratg]

@natemcmaster So it'll be netstandard1.5 only? I think it should be fine -- any objections @davidfowl?

[natemcmaster]

Dropping netstandard1.0 means dropping:

• Universal Windows Platform 10
• Windows Phone 8.0, 8.1
• Windows Phone Silverlight

[pranavkm]

Fixed as part of targeting netstandard2.0 (c0e09fd).