Update Couchbase.nuspec .NET Core dependencies

I believe that we need to update the Couchbase.nuspec dependencies (unless they are pciked up automagically?). Here are the dependencies:

<dependencies>
<group>
<dependency id="Microsoft.CSharp" version="4.3.0"/>
<dependency id="Microsoft.Extensions.Logging.Abstractions" version="1.1.0"/>
<dependency id="Microsoft.NETCore.Portable.Compatibility" version="1.0.1"/>
<dependency id="NETStandard.Library" version="1.6.1"/>
<dependency id="Newtonsoft.Json" version="9.0.1"/>
<dependency id="System.Globalization.Extensions" version="4.3.0"/>
<dependency id="System.Net.Http" version="4.3.0"/>
<dependency id="System.Net.NameResolution" version="4.3.0"/>
<dependency id="System.Net.Primitives" version="4.3.0"/>
<dependency id="System.Net.Security" version="4.3.0"/>
<dependency id="System.Net.Sockets" version="4.3.0"/>
<dependency id="System.Reflection.TypeExtensions" version="4.3.0"/>
<dependency id="System.Runtime.Serialization.Primitives" version="4.3.0"/>
<dependency id="System.Threading.Tasks.Parallel" version="4.3.0"/>
<dependency id="System.Threading.Thread" version="4.3.0"/>
</group>
</dependencies>