Update ImageResizer sample, remove System.Drawing
Update ImageResizer sample, remove System.Drawing

Since automatic NuGet restore now works, remove the commented out code that used System.Drawing. Also cleaned up "using" statements that weren't needed.
davidlai-msft/azure-webjobs-sdk-templates,soninaren/azure-webjobs-sdk-templates,mattchenderson/azure-webjobs-sdk-templates,mattchenderson/azure-webjobs-sdk-templates,soninaren/azure-webjobs-sdk-templates,mattchenderson/azure-webjobs-sdk-templates,Azure/azure-webjobs-sdk-templates,Azure/azure-webjobs-sdk-templates,Azure/azure-webjobs-sdk-templates,Azure/azure-webjobs-sdk-templates,mattchenderson/azure-webjobs-sdk-templates,davidlai-msft/azure-webjobs-sdk-templates,davidlai-msft/azure-webjobs-sdk-templates,davidlai-msft/azure-webjobs-sdk-templates,mattchenderson/azure-webjobs-sdk-templates,Azure/azure-webjobs-sdk-templates,davidlai-msft/azure-webjobs-sdk-templates,mattchenderson/azure-webjobs-sdk-templates,Azure/azure-webjobs-sdk-templates,soninaren/azure-webjobs-sdk-templates