Remove --style flag from yapf

The --style flag accepts different types of input. From their documentation - "accepts one of the predefined styles (e.g., pep8 or google), a path to a configuration file that specifies the desired style, or a dictionary of key/value pairs."

By not explicitly specifying the --style flag, yapf will look for the following, in that order

1. In the [style] section of a .style.yapf file in either the current directory or one of its parent directories.
2. In the [yapf] secionf of a setup.cfg file in either the current directory or one of its parent directories.
3. In the ~/.config/yapf/style file in your home directory.

src/beautifiers/yapf.coffee

@@ -16,7 +16,6 @@ module.exports = class Yapf extends Beautifier
   beautify: (text, language, options) ->
     @run("yapf", [
       "-i"
-      ["--style=pep8"]
       tempFile = @tempFile("input", text)
       ], help: {
         link: "https://github.com/google/yapf"