GitLab

* add copyright header

* change # to // for cpp files

* fix the code style of yapf 0.29

* fix flake8

* add yapf and isort to travis

* minor formatting

* remove blank lines

* skip unit tests for progressbar when python2

* update travis to ubuntu 16.04

* use a newer version ffmpeg

* add -y to add-apt-repository

* flow_warp_c

* flow_warp_c

* beautify format

* beautify format

* beautify format

* beautify format

* add Cython

* modify

* fix details

* fix details

* fix type