Fixed hierarchical softmax comments

Adding comments to a number of areas.

Added a few comments to the analogies code.

Updating README to mention CBOW comments

Added comments for CBOW with negative sampling.

Added notes on the layer weights variables

Merge branch 'master' of https://github.com/chrisjmccormick/word2vec_commented

Added detailed comments for unigram table

Fixing header formatting

Added discussion of the word2phrase tool.

Added comments to the phrase detection tool.

Fixed a typo, updated explanation of puting newline back.

Added links to original source and my tutorial.

Updated function description; recommented hiding code blocks.

Commented the skip-gram negative sampling training code.