Created Unassigned: Please add support of netcoreapp1.0 [15571]

Hi,

Currently EPPlus cannot be used as part of the .NET Core application. I get this error:
```
Restoring packages for D:\Projects\ConsoleApp1\ConsoleApp1.csproj...
Package EPPlus 4.1.0 is not compatible with netcoreapp1.0 (.NETCoreApp,Version=v1.0). Package EPPlus 4.1.0 supports:
- net35 (.NETFramework,Version=v3.5)
- net40 (.NETFramework,Version=v4.0)
One or more packages are incompatible with .NETCoreApp,Version=v1.0.
Package restore failed. Rolling back package changes for 'ConsoleApp1'.
========== Finished ==========
Time Elapsed: 00:00:00.5826719
```

Please add support of .NET Core apps