Dependency not listed in the NuGet package

[vrescobar]

When I install Backendless.Net from the NuGet I see it displays no dependency in the list, just in the readme file, which is it inconvenient as it will fail to compile the project.

To reproduce create a new Xamarin Forms, try to add the Backendless package and try to compile.

When installed manually it will fail as described in issue #14

[holailusoria]

This has been fixed