updated server.py to create dir if not available

fix #2 
> 1) what's the point in a config file if the user can't change locations.

```
>>> sql_dir = os.path.dirname("~/foo")
>>> os.path.exists(sql_dir)
False
```

> 2) I'm ok with making this only inside centinel_home, but we need to add a comment that users must create other directories if they use them.

this is too much discussion for a 4 line change. i just merged.