* [LLVM] Initial support for codegen LLVM.

* Fix the naming issue of codegen

* [PASS] Change IRVisitor interfaces to function override

* [PASS] Change IRMutator interfaces to overloadable function

* [FUSION] add Fusion(Schedule)

* [FUSION] rename to AutoFuseEwise, detect whether the stage has been scheduled

* [FUSION] change to visitor pattern

* [FUSION] rename filename

* [FUSION] fine-tune the interface

* [FUSION] typo

* move elem_wise to schedule

* rename test function

[TEST/PYTHON] Add unittest folder, add a build pipeline. Rename Buffer.ptr to Buffer.data to be consistent with Array. (#29)

* [CODEGEN] CUDA/OPENCL pipeline complete

* Hide TVMType by str in frontend

* [CODEGEN] Add LoweredFunc, MakeAPI and SplitHostDevice

* update halideir

* [RUNTIME] Finish GPU runtime and python interface

* fix travis test

* fix build

* [PASS] Export simplify and equal to python

* fix naming convention

* [RUNTIME] Add interface header of runtime

* fix mac build

* [LANG] Include buffer semnatics, introduce pylint

* Refactor inline add support for buffer indexing

* fix doc

* [LANG] Change Schedule->Stage, Use Schedule for global schedule

* add numpy as dep

* add numpy installation, temporary disable osx

* [PASS] Schedule Ops init working version

* bugfix in PassUp