Export __version__

**Describe the Bug**

`apex.__version__` is not exported.

**Minimal Steps/Code to Reproduce the Bug**

```python
import apex
apex.__version__
```

result:

`AttributeError: module 'apex' has no attribute '__version__'`

**Expected Behavior**

expected result: `'0.1'`

**Environment**

`apex` version `0.1`