Fix the incompatibility of gif saving

fix srn_postprocess

When cv2.imwirte() saves ".gif", it will cause _error: (-2:Unspecified error) could not find a writer for the specified extension in function 'cv::imwrite_'_. We add an if statement to check whether the saving file format is ".gif" so as to avoid the error.

use pretrained_model for eval

修正拼写错误

add faq 20210322

add faq 20210316

Update joinus.png

修改拼写错误

enable memory optim

rename language abbreviations

Update joinus.png

* update FAQ

Release/2.0

fix label error