add max_p to psnr (#240)
add max_p to psnr (#240)

* add max_p to psnr

* Update symbolic_functions.py

* fix liniting and remove name_scope

eyaler/tensorpack,haamoon/tensorpack,ppwwyyxx/tensorpack,eyaler/tensorpack,ppwwyyxx/tensorpack,haamoon/tensorpack,haamoon/tensorpack