segmentation fault when using `__contains__` on a FAM `values()`

```
>>> import automap
>>> am = automap.AutoMap(('a', 'b'))
>>> test = []
>>> test in am.values()
False
>>> test
[]
>>> print(test)
Segmentation fault (core dumped)
```
This is due to calling `Py_DECREF(other)` in `famv_contains()`. This is corrected in my current branch (#16)

