Hypergraphs with Attention on Reviews for Explainable Recommendation (#600)

* Init method

* Example file

* Added HypAR

Added hyper and its functions.

* Added dataset standard files and virtual env names to ignore

* Create graph comments

* Flock comments

* Graph wrapper comments

* ao embedding comments

* Remove learned ui embeddings

* Learned embedding and norm comments

* fit comments

* Removed unused code

* Comments on main file

* Removed more and comments

* More comments

* More comments

* Updated readmes

* Fix dataset name

* Reference fix

* Path fix

* Removed example

* Removed HypAR from examples readme

* Styling

* Added hypar doc string

* Removed spacing

* Added paper link

* Moved docstrings to earlier

* Simplified model type

* Added paper reference

* Added lightgcn as part of HypAR

* Updated url

* Fix double normalize of first layer