Fix [Error 22] under Windows reading .editorconfig

Under windows system, if the .editorconfig is not CRLF ended, after
reading file using `file.readline()`, the `file.tell()` will give 
negative values, which at last raises IOError: [Errno 22] Invalid 
argument. This patch open config files in "universal newlines" mode,
which treat all line endings as '\n', hopefully fixes that issue.