problem accessing sqlite databases with full path

Hi all,
I'm trying to use the SQLReader class in python script widget to access a sqlite database placed in a different path than orange itself. Here's the code:

```
from Orange.data.sql import *
r = SQLReader()
r.connect('sqlite:///d:/path/to/database.db/')
```

and this is the log:

```
Running script:
Traceback (most recent call last):
File "", line 1, in
File "", line 4, in
File "[...]\Orange\utils\__init__.py", line 214, in wrap_call
return func(*args, **kwargs)
File "[...]\Orange\data\sql.py", line 195, in connect
(self.quirks, self.conn) = _connection(uri)
File "[...]\Orange\data\sql.py", line 141, in _connection
return (quirks, dbmod.connect(host))
ValueError: database parameter must be string or APSW Connection object
```

Looking at the source code it seem that the connection string is not treated at it should since
[line 15](https://github.com/biolab/orange/blob/master/Orange/data/sql.py#L15) is handling the third slash incorrectly.