update to readme to include info about .GetGridHtml()
update to readme to include info about .GetGridHtml()

hfloyd/Skybrud.Umbraco.GridData,skybrud/Skybrud.Umbraco.GridData,hfloyd/Skybrud.Umbraco.GridData,nvisage-gf/Skybrud.Umbraco.GridData,nvisage-gf/Skybrud.Umbraco.GridData