Respect project editorconfig settings

If a project directory has a .editorconfig file, yapf should use available style settings from there instead of falling back to hard-coded defaults. For instance, if the project .editorconfig has `[*.py] indent_size = 2` then yapf should not indent by 4 (unless it has an explicit indent_width = 4).

Important settings to respect: `indent_size`, `indent_style`, and `max_line_length`.