Made Postgresql specific insert handle entities with no primary keys.

Dapper.Contrib/SqlMapperExtensions.cs

@@ -190,6 +190,8 @@ private static string GetTableName(Type type)
 			sb.Append(") ");
 			long id = 0;
 #if POSTGRESQL
+			if (keyProperties.Count() > 0)
+			{
 				sb.Append(" RETURNING ");
 				for (var i = 0; i < keyProperties.Count(); i++)
 				{
@@ -207,6 +209,9 @@ private static string GetTableName(Type type)
 					if (id == 0)
 						id = Convert.ToInt64(value);
 				}
+			}
+			else
+				connection.Execute(sb.ToString(), entityToInsert, transaction: transaction, commandTimeout: commandTimeout);
 #else
             connection.Execute(sb.ToString(), entityToInsert, transaction: transaction, commandTimeout: commandTimeout);
             //NOTE: would prefer to use IDENT_CURRENT('tablename') or IDENT_SCOPE but these are not available on SQLCE