Swift 3 `String` extension to convert text file contents to lines, even if file is DOS format

String+SeparatedIntoLines.swift

extension String {
    func separatedIntoLines() -> [String] {
        var lines: [String] = []
        let wholeString = self.startIndex..<self.endIndex
        self.enumerateSubstrings(in: wholeString, options: .byLines) { 
            (substring, range, enclosingRange, stopPointer) in
            if let line = substring {
                lines.append(line)
            }
        }
        return lines
    }
}