Option to disable parsing of toml files needed

If there is a tmol file in the current directory yapf try to parse it. and fails.

I have a lot of projects using pyproject.toml files and in them I can not use yapf in vim without changing to a other directory and edit from there ...

```
❯ ls -alh pyproject.toml
-rw-r--r-- 1 xxx yyy 1,4K 2 Dez 11:38 pyproject.toml
❯ yapf ~/tmp/foo.py
yapf: toml package is needed for using pyproject.toml as a configuration file
```
It works in a dir with no pyproject.toml file
```
❯ ls -alh pyproject.toml
ls: pyproject.toml: No such file or directory
❯ yapf ~/tmp/foo.py
x = {'a': 37, 'b': 42, 'c': 927}
```