Update paddle serving app __init__.py

fix predict return

add cascade rcnn

update readme and image_rpc_client

Update util.go

get numpy array from ModelRes without copy

Merge branch 'develop' of https://github.com/PaddlePaddle/Serving into try-to-get-numay_array-from-ModelRes

update compile doc

Fix numpy predict

add mkl argument

fix criteo ctr with cube doc

build whl for different python

add switch for ir pass

fix doc && centos6 dockerfile

fix #542: add Exception for use numpy with lodtensor

refine inference model to serving api