GitLab

* let progress goes to stderr
Signed-off-by: lizz <lizz@sensetime.com>

* Add argument file=sys.stdout
Signed-off-by: lizz <lizz@sensetime.com>

* For the sake of the stupid pytest
Signed-off-by: lizz <lizz@sensetime.com>

* line width < 120 is anti-humane
Signed-off-by: lizz <lizz@sensetime.com>

* flake8
Signed-off-by: lizz <lizz@sensetime.com>

* Lets try
Signed-off-by: lizz <lizz@sensetime.com>

* track progress of iter&enum

* reformat

* reformat with yapf

* add unitest

* add doc, and deprecate track_enum_progress

* update docs & comments

* 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