needs pkg_resources in Depends

```
hopa(/home/yoh/proj/repronim/neurodocker-cases/fslanal):~/proj/repronim/neurodocker-cases
$> DISPLAY=:0 /usr/bin/fsleyes 
Traceback (most recent call last):
  File "/usr/bin/fsleyes", line 6, in <module>
    from pkg_resources import load_entry_point
ImportError: No module named pkg_resources
```