Filename completion completes directory too deep

``` .py
tom-mba:~ tomb$ bpython
bpython version 0.13-363 on top of Python 2.7.9 /usr/local/opt/python/bin/python2.7
>>> '/e
```

and then tab becomes
`/etc/AFP.conf`
when it ought to be
`/etc/`
I think. The current behavior is kind of reasonable (selecting the first selection immediately, allows you to tab through the rest) but isn't good and doesn't match bash.
