修复git命令报错

1.报错信息：fatal: remote origin already exists.
 
  修复命令：git remote rm origin

2. Error : git push origin master

          error: src refspec master does not match any.
          error: failed to push some refs to 'https://github.com/imwalking/pythonlesson'
 root:    No README.md
          git pull --rebase origin master
          git push origin master