http://colah.github.io/posts/2014-07-NLP-RNNs-Representations/
https://www.quora.com/What-is-the-definition-of-word-embedding-word-representation
https://www.gavagai.se/blog/2015/09/30/a-brief-history-of-word-embeddings/
GOOD: https://iksinc.wordpress.com/tag/continuous-bag-of-words-cbow/