Update using.rst (#938)
Update using.rst (#938)

Summary:
Added data format for the tracks.csv file in order to help other people using that file

Pull Request resolved: https://github.com/mapillary/OpenSfM/pull/938

Reviewed By: YanNoun

Differential Revision: D38908516

Pulled By: fabianschenk

fbshipit-source-id: 307207958b36f87290695503d73199e1fab8506f

mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM