Add support to read log files of  SummaryWriter

The log of training is written by `SummaryWriter`. It is not possible to change file name and format, but we can add timestep as suffix, see [filename_suffix](https://docs.pytorch.org/docs/stable/tensorboard.html#torch.utils.tensorboard.writer.SummaryWriter). Also we can add a util function to read the log file using [tbparse](https://github.com/j3soon/tbparse). 