returned array has wrong length

Python: python 3.5
pysais: master

```
from sklearn.datasets import fetch_20newsgroups
import pysais
s = '$'.join(fetch_20newsgroups().data)
sa = pysais.sais(s)
print(len(s))
print(len(sa))
```

expected output:
```
22065807
22065807
```

actual output:
```
22065807
22065930
```