url name teams:join_name -> teams:join
team join url : /teams/<team id>/join
url name : maketeam -> new, accept_request_... -> accept, join_team -> join
teams' views.py : url name : maketeam -> new
home.html : url name : maketeam -> new, accept_request_... -> accept, join_team -> join
buildbuild/urls.py : url /teams/ in teams/urls.py, not buildbuild/urls.py
teams/urls.py : url /teams/ in teams/urls.py, not buildbuild/urls.py