Bump up dependency versions and clean out unused ones.

* These old versions were causing some major issues when publishing for
  netcoreapp2.0.

src/ImGui.NET/ImGui.NET.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Description>A .NET wrapper for the dear ImGui library.</Description>
-    <AssemblyVersion>0.3.0</AssemblyVersion>
+    <AssemblyVersion>0.3.1</AssemblyVersion>
     <Authors>Eric Mellino</Authors>
     <TargetFramework>netstandard1.1</TargetFramework>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
@@ -16,12 +16,9 @@
     <DocumentationFile Condition="'$(Configuration)' == 'Release'">$(OutputPath)\ImGui.NET.xml</DocumentationFile>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="System.Diagnostics.Debug" Version="4.3.0" />
-    <PackageReference Include="System.Numerics.Vectors" Version="4.3.0" />
-    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.3.0" />
-    <PackageReference Include="System.Runtime.Extensions" Version="4.3.0" />
-    <PackageReference Include="System.Runtime.InteropServices" Version="4.3.0" />
-    <PackageReference Include="System.Buffers" Version="4.3.0" />
+    <PackageReference Include="System.Numerics.Vectors" Version="4.4.0" />
+    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.4.0" />
+    <PackageReference Include="System.Buffers" Version="4.4.0" />
   </ItemGroup>
   <ItemGroup>
     <Content Include="..\..\deps\cimgui\win-x64\cimgui.dll">