Fix Version equality
_The documentation is not available anymore as the PR was closed or merged._
I think `Version` equality should align with other similar cases in Python, like:
```python
In [1]: "a" == 5, "a" == None
Out[1]: (False, False)

In [2]: "a" != 5, "a" != None
Out[2]: (True, True)
```

With this PR, we will get:
```python
In [3]: Version("1.0.0") == 5, Version("1.0.0") == None
Out[3]: (False, False)

In [4]: Version("1.0.0") != 5, Version("1.0.0") != None
Out[4]: (True, True)
```

Note I found this issue when `doc-builder` tried to compare:
```python
if param.default != inspect._empty
```
where `param.default` is an instance of `Version`.