README.md

The format of the layer.json file is as below:
```
{
    "fmap_width": "width of output fmap",
    "fmap_height": "height of output fmap",
    "input_fmap_channel": "input channel number",
    "output_fmap_channel": "output channel number",
    "window_width": "width of the filter window",
    "window_height": "height of the filter window",
    "batch_size": "number of image in a batch",
    "stride_width": "width of stride, default 1",
    "stride_height": "height of stirde, default 1"
}
```