Update CONTRIBUTing.md

Move Fluid C++ code from /paddle to /paddle/fluid

move paddle/pybind/pybind.h to paddle/fluid/pybind/pybind.h, and cancel the test_parallel_op temporary

* Added an elementary test case for CSP

* removed input

* Rename test file to avoid running in CI

* Fix YAPF error

* Remove one line function handler

* Add unit-test and example

* Fix type error

* Fix unit test cases

* Fix init error for cudaplace

* Change unit-test options

* initial commit

* fix bug

* end of file fix

* address comments

Rewrite mixed_vector.h

Remove 'numel' checker in compare op

* initial commit

* minor fix

* remove redundency

* address comments

Delete "API" section from "Documentation"

create optimize block in pserver program

Fix the bias of fc when num_flatten_dims is not 1 in fluid layers