Thanks @hlu1 and @tqchen, this is now merged.

* Add eager simplication for FloatImm

* fix

* fix lint

* Fix gcc warning

* fix

* Add test case

* nms data race solved

* tst_topi_vision reference results are gonna be updated in PR #2353

* proposal nms_ir updated

* alter_op_layout for x86

* cleanup

* cleanup

* fix lint

* fix lint

* fix lint

* fix lint

* change support level

* change other support levels

* check in

* update build and run

* First pass on ADTs

* Add doc string for tag field

* Visit constructors in TypeVisitor for TypeData

* Add to description of type call

* Add type call to type solving and unification

* Make type mutator for typecall consistent with others (only create new node if there's a change)

* Ensure kindchecking can handle type calls and typedata

* Fix bad nesting in module constructor

* Correctly construct call in typecall test

* Add call override for ordinary vars (do we want this?)

* Remove generalization hack from type inference because it was breaking ADT constructors

* Check that there are no free type vars in exprs after inferring type

* Free var checks need module because of ADT constructors

* Typecall test can't have unbound type var, make it global

* Uncomment tmap test and remove comments about failing to infer ret type; those work now

* Put in dummy visits for ADTs in graph runtime codegen to placate pylint

* Fix Relay type infer test module constructor

* Mark override for TypeCallNode in type solver

* Ensure free vars check treats patern vars as bound

* Run interpreter in more ADT test cases

* Refactor kind check to return the kind, like typechecking

* Fix invalid typecall in test

* Add kind check to type inference, do not use nulls in func_type_annotation()!

* Redundant whitespace

* Make TypeData a separate kind

* Make ADT handles a separate kind too, document calling convention better

* Remove nats and tree from prelude, move to test, document prelude

* Restore and document nat and tree to prelude, add more tree tests

* Add alpha equality tests for match cases, fix variable binding bug

* Add more kind check tests for ADTs

* Add more tests for finding free or bound vars in match exprs

* Add unification tests for type call

* Update main() for alpha equality tests

* Add simple type inference test cases for match exprs and ADT constructors

* Add more ADT interpreter tests

* Allow incomplete types when typechecking match cases

* Type inference for pattern vars should use the type annotation if it's there

* Two more specific test cases for ADT matching

* Add option ADT to prelude

* Fix broken reference to kind enum

* Fix rebase snags

* Do not attach checked types to constructors

* More docstrings for module fields

* Use proper wrapper for indexing into module type data

* checked_type for constructors is not populated

* Expand type call docstring

* Rename PatternConstructor con field

* Use error reporter for pattern constructor case

* Condense error reporting in kind check, use error reporter

* Expand docstrings and rename ADT fields

* Rename 'option' ADT to 'optional' for consistency with Python

* Add various list iterators and utility functions to prelude

* Add smoke tests for new iterators in prelude

* Add concat to prelude

* Add smoke test for concat

* Correct docstrings in prelude

* Ensure that type defs are written in module initialization

* Various requested renamings

* Correct rebase snags

* Add kind check tests for ref types

* Update the main() for kind checking tests

* Version 0.5

* update version.py

* update news

* update news

* update news

* move

fix test

fix lint

fix test

add more code

fix lint

better type infer ability

* fix build

* address comment

* update titles to reflect tutorial content (nnvm vs. relay)

* move things around

* fix typo

* fix storage_rewrite bug when input is big

* cast when necessary

* simplification

* simplification

* int64->uint32

* revert uint32->int64

* [TOPI][CUDA] Add faster-rcnn proposal op

* Fix doc

* Add global barrier

* Use vthread in argsort

* Update sort and nms ir

* Fix lint

* Update sort ir in ssd nms

* a preliminary version is done?

* we no longer need the redundant hybrid/api.py

* support assert stmt

* cast supported

* intrin -> runtime; util is mainly in charge of compilation time

* assert statement

* fix python lint

* fix cpp lint

* on the way to module

* rollback .cc

* fix typo, no direct expose then

* @vinx13 ceil is added i guess?

* wip...

* temp commit

* fix import

* i preliminary version is done?

* on the way to build hybrid module

* nearly fixed...

* dumped python are equiv as original python

* on the way to bootstrap

* cpu bootstrap done

* bootstrap!

* fix lint

* fix doc

* resolve some review concerns

* support load/save

* fix lint

* thanks to xqdan fixed my typo

* fix build, make dump non-optional

* add vthread

* jesus why i added this

thanks @icemelon9, this is merged

Remove exception trail in tf parser error message

Fix lint

Fix comments

TF parser: return the consistent error message to error handler

Optimize move semantics of NodeEntry reducing copies of shared_ptr which causes atomic contention (#2576)