GitLab

* Add weight based edge sampler

* Can run, edge weight work.
TODO: test node weight

* Fix node weight sample

* Fix y

* Update doc

* Fix syntex

* Fix

* Fix GPU test for sampler

* Fix test

* Fix

* Refactor EdgeSampler to act as class object not function that it
can record its own private states.

* clean

* Fix

* Fix

* Fix run bug on kg app

* update

* update test

* test

* Simply python API and fix some C code

* Fix

* Fix

* Fix syntex

* Fix

* Update API description