update nuget packages to reference ocelot logo from GitHub

Author: TGP

src/Ocelot/Ocelot.csproj

@@ -9,7 +9,7 @@
     <PackageId>Ocelot</PackageId>
     <PackageTags>API Gateway;.NET core</PackageTags>
     <PackageProjectUrl>https://github.com/ThreeMammals/Ocelot</PackageProjectUrl>
-    <PackageIconUrl>http://threemammals.com/images/ocelot_logo.png</PackageIconUrl>
+    <PackageIconUrl>http://github.com/images/ocelot_logo.png</PackageIconUrl>
     <RuntimeIdentifiers>win10-x64;osx.10.11-x64;osx.10.12-x64;win7-x64</RuntimeIdentifiers>
     <GenerateAssemblyConfigurationAttribute>false</GenerateAssemblyConfigurationAttribute>
     <GenerateAssemblyCompanyAttribute>false</GenerateAssemblyCompanyAttribute>