Can't run example code

Although I wasn't able to build on MacOS, the project built on Linux. However, I try to follow the example steps, and it breaks when I try to build a model:

```
build/difacto data_in=data/gisette_scale val_data=data/gisette_scale.t lr=.02 V_dim=2 V_lr=.001
```
The error is:
```
terminate called after throwing an instance of 'dmlc::ParamError'
what(): Required parameter batch_size of int is not presented
Aborted (core dumped)

```