* to simple
* WIP: multigraph flag
* graph index refactor; pass basic testing
* graph index refactor; pass basic testing
* fix bug in to_simple; pass torch test
* fix mx utest
* fix example
* fix lint
* fix ci
* poke ci
* poke ci
* WIP
* poke ci
* poke ci
* poke ci
* change ci workspace
* poke ci
* poke ci
* poke ci
* poke ci
* delete ci
* use enum for multigraph flag
* test basics
* batched graph & filter, mxnet filter fix
* frame and function; bugfix
* test graph adj and inc matrices
* fixing start = 0 for mxnet
* test index
* inplace update & line graph
* multi send recv
* more tests
* oops
* more tests
* removing old test files; readonly graphs for mxnet still kept
* modifying test scripts
* adding a placeholder for pytorch to reserve directory
* torch 0.4.1 compat fixes
* moving backend out of compute to avoid nose detection
* tests guide
* mx sparse-to-dense/sparse-to-numpy is buggy
* oops
* contribution guide for unit tests
* printing incmat
* printing dlpack
* small push
* typo
* fixing duplicate entries that causes undefined behavior
* move equal comparison to backend
Zihao Ye