Fix sgd trainer document error.

Add a c-api interface to get the output of a specified layer.

Fix bug of enforce when dladdr not found

* Wrong Printf format before

add shared warpctc lib in whl

Fix invalid paddle executable file path with pip install  

Implement EigenCudaStreamDevice

use param header to save mkldnn format info

* add clang-format with version check 3.8

* improve doc

* insert rnn's backward into Backward()

* add device_context into backward_test

* large model train note

* update

* update doc

fix crash when disable WITH_SWIG_PY

build documentation don't need install Paddle before

Fix local recordio reader

add shared mkl lib in whl

* make stepnet member

* add pybind support

* fix Inputs Outputs

* remove unique_ptr

change operator public to protected

scatter update implemented