something wrong with heroku,so i input rm -rf /usr/bin/heroku,rm -rf /usr/local/heroku/bin/heroku,and input sudo apt-get remove heroku-toolbelt,when i have reinstalled heroku-toolbelt,the /usr/local/heroku/bin/heroku/ folder is not found,also /usr/bin/heroku,so when i input heroku login command in the terminial,it display heroku:command not found,why?can you tell me how to fix it,thank you!