Selecting all posts created by user that actual user follows
Let's focus on the selecting.

class MyPage(ListView):
    model = Post

    def get_queryset(self):
        posts = []
        for user in self.request.user.followers.all():
            for post in Post.objects.filter(author=user.followed):
                posts.append(post)

        return posts


This is a bit convoluted: you're performing a lot of queries (depending on how many followers a user has). Ideally you'd like to perform just one query.

Also, get_queryset looks like it will return a queryset, instead of a list.

class MyPage(ListView):
    model = Post

    def get_queryset(self):
        return Post.objects.filter(author__followers__follower__id=self.request.user.id)


Should work just as well, and returns an actual queryset. (I'm not sure if I got the exact syntax right, please look at https://docs.djangoproject.com/es/1.9/topics/db/queries/#spanning-multi-valued-relationships if it does not work).