Update installation.md 

Update sentence_sim.md 

 add unitest, config, fix ernie_gen bugs and add ernie_tiny_couplet (P… …addlePaddle#782)

Update release.md 

modify_readme_contents,test=develop (PaddlePaddle#480) 

update cmd_intro doc (hub download) (PaddlePaddle#453) update cmd_intro doc (hub download)

Update autofinetune.md 

Update autofinetune.md 

Merge pull request PaddlePaddle#358 from ShenYuhan/serving_ma turn i_img on

Create cache directory automaticly