Fix fs.lopen in Python 2, to use io module
Fix fs.lopen in Python 2, to use io module

In Python 2, `lopen` is failing when trying to open a file in bynary
mode:

```
(Pdb) locals()
{'errors': None, 'inspect': <module 'inspect' from '/usr/lib/python2.7/inspect.pyc'>, 'encoding': None, 'newline': None, 'filename': u'session.ini', 'flags': 6, 'closefd': True, 'buffering': -1, 'blocking': False, 'mode': u'ab+'}
(Pdb) open(filename, mode=mode, buffering=buffering, encoding=encoding, errors=errors, newline=newline, closefd=closefd).__enter__()
*** ValueError: binary mode doesn't take an encoding argument
(Pdb) io.open(filename, mode=mode, buffering=buffering, encoding=encoding, errors=errors, newline=newline, closefd=closefd).__enter__()
<_io.BufferedRandom name=u'session.ini'>
```

As the current `open` context manager already uses the `io.open`
function, it seems just like a typo.

pyblub/pyload,pyblub/pyload