setup.py: PEP8ify

Before:

```
 ❯ pep8 --quiet --statistics setup.py
setup.py
2       E121 continuation line indentation is not a multiple of four
1       E222 multiple spaces after operator
1       E231 missing whitespace after ':'
38      E251 unexpected spaces around keyword / parameter equals
```

After:

```
 ❯ pep8 --quiet --statistics setup.py

 ❯ echo $?
0
```