GitLab

* add pyupgrade

* add options for pyupgrade

* minor refinement

* [Fix] fix train example

* [Fix] fix a detail in train example and add warning in MMDP

* [Fix] fix docstring

* [Fix] fix docstring

* [Fix] Fix example

* rename Net to Model

* support training without gpu in example

* modify according to comment

* replace data path with relative path

* Assign different priority to default hooks, and add custom hook register in base runner.

* Add custom hook register in example train file

* Add unittest of custom hook

* Code format

* update doc formats

* update docstring

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

* 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