Settings override via project config

Example `my_project.sublime-project`:

```json
{
	"folders":
	[
		{
			"path": "/home/guest/Pythons"
		}
	],
    "settings": {
        "isort": {
            "known_first_party": "my_project",
            "default_section": "THIRDPARTY",
            "multi_line_output": 5,
            "indent": "    "
        }
    }
}
```