Update README.md

[freddy1020]

1. miss a comma after the introductory clause
2. "the way" -> "how"
3. rewrite these three sentence
4. "is the capability to set the color of one pixel" maybe not be clear to read, so I change this to "is the ability to set one pixel's color."
5. "github" -> "Github" I hope these changes to the documentation will contribute to the project！

[DouYuexi]

我已经收到您的邮件了，我将会尽快处理，保持联系！