Add awesome-transformer

[SkyAndCloud]

awesome-transformer, should classified into Deep Learning。 Transformer is a powerful model applied in sequence to sequence learning. However, when I was using transformer as my baseline in NMT research I found no good & reliable guide to reproduce approximate result as reported in original paper(even official tensor2tensor implementation), which means my research would be unauthentic. I searched on the Internet, found some implementations, obtained some performance-reproducable approaches and other learning materials, which eventually formed this project. I hope more researchers can benefit from it.

[sindresorhus]

Make sure you follow https://github.com/sindresorhus/awesome/blob/master/pull_request_template.md, then do a pull request.