Merge pull request SixLabors#560 from carbon/memory-rc1

Update System.* deps to 4.5.0-rc1

Author: JimBobSquarePants

tests/ImageSharp.Tests/ImageSharp.Tests.csproj

@@ -27,8 +27,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="Microsoft.CSharp" Version="4.4.1" />
-    <PackageReference Include="System.Numerics.Vectors" Version="4.5.0-preview2-26406-04" />
-    <PackageReference Include="System.Drawing.Common" Version="4.5.0-preview2-26406-04" />
+    <PackageReference Include="System.Drawing.Common" Version="4.5.0-rc1" />
     <PackageReference Include="xunit" Version="2.3.1" />
     <PackageReference Include="xunit.runner.console" Version="2.3.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.3.1" />