Fix warnings: classic int division & unclosed file

Hi,
there are some annoying warnings if I import charade in my project.
```
DeprecationWarning: classic int division
```

When I run tests for charade I get some extra warnings.
```
test.py:28: ResourceWarning: unclosed file <_io.BufferedReader name='...'>
  for line in open(self.file_name, 'rb'):
```

I use commands bellow to run python script:
```
python -tt -Wall -3 test.py
python3 -tt -Wall test.py
```