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.