jquery bug fixes / refactoring jquery + erb/routes

The ||= will only assigned the User.find(session[:user_id]) to @current_user if it is nil. Otherwise, it will leave it alone if it already has a value inside it. 

It has the same effect as the following:

if !@current_user
  @current_user = User.find(session[:user_id])
else
  @current_user
end