* Add paper conference link and mmcv install docs

* Update contributing

* fix #4181, invalid link in readme for maskrcnn cityscapes

* undo

* add config for paa_r50_fpn_mstrain_3x_coco.py

* reformat for CI building

* add config paa_r101_fpn_mstrain_3x_coco.py

* add r50 and r101 multiscale training 3x performance

* add pretrained model link

* Add markdown lint in pre-commit hook

* add markdown lint

* fixed typos

* replace url with download

* update to http

* implement PAA assign

* unpate setup.cfg

* fix multiply ioupred with clsscore

* add score voting

* add 2x and 101 configs

* add voting return

* make sklearm optional

* remove sklearm in setup.cfg

* separate pos loss calculation from reassign

* add unitest and readme

* add model url

* fix reduction and doc

* add 1.5x

* fix config base

* add r50 1.5x results

* mock skm

* change according to comment

* remove return none

* add universal partition interface

* fix docstr

* fix docstr

* fix docstr