Cell Separator Inset:

For iOS 7.0:
============

if ([tableView respondsToSelector:@selector(setSeparatorInset:)]) {
    [tableView setSeparatorInset:UIEdgeInsetsZero];
}

or

[tableView setSeparatorInset:UIEdgeInsetsZero];
   
   
For iOS 8.0:
============

tableView.layoutMargins = UIEdgeInsetsZero;
cell.layoutMargins = UIEdgeInsetsZero;


======================================================


-(void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
{
    // Remove seperator inset
    if ([cell respondsToSelector:@selector(setSeparatorInset:)]) {
           [cell setSeparatorInset:UIEdgeInsetsZero];
    }

    // Prevent the cell from inheriting the Table View's margin settings
    if ([cell respondsToSelector:@selector(setPreservesSuperviewLayoutMargins:)]) {
        [cell setPreservesSuperviewLayoutMargins:NO];
    }

    // Explictly set your cell's layout margins
    if ([cell respondsToSelector:@selector(setLayoutMargins:)]) {
        [cell setLayoutMargins:UIEdgeInsetsZero];
    }
}