Doesn't currently work with connect 3.0

```
Cannot read property 'session' of undefined

{ column: 42,
       file: '~/code/location/node_modules/connect-session-file/lib/connect-session-file.js',
       function: '',
       line: 9,
       method: null,
       native: false }
```

Fixing the require statement would be the better option probably but as a quick fix this should work out.