support anakin for only-cpu environment

Clean

refine fusion lstm/peephole and fusion gru

* add save_inference_model for Trainer

* add comment

* update comment

* fix mac compile

* add unit test

* update API.spec

* revert cpplint-cpp-source

add error info for nccl not found

fix parallel run dist unit test

Disable feed_fetch_unit_test temporarily

fix cuda9 docker build

Open python35 ci

Use double to reduce

* Add intermediate

* fix flatten/squeeze/unsqueeze

* Considering compatibility issues, we could not fix the origin op

* follow comment

* reset the shape of XShape

 add multi-thread ut for ditu-rnn

* rmsprop optimizer support v1 mode

* typo

* optimize code

* refine code

* optimize unit test

* update test_rmsprop_op.py

* update formula of rmsprop

* optimize document

* update API.spec for RMSPropOptimizer

* add default value to check_output_with_place equal_nan