About make_batch of NNLM

```python
input = [word_dict[n] for n in word[:-1]] # create (1~n-1) as input
target = [word_dict[word[-1]]]
```

it constraints the length of input and n_step. I think the following example is even better

```python
for i in range(len(words) - window_size + 1):`
` x_train.append(words[i: i + window_size - 1])`
`y_train.append(words[i + window_size - 1])
```