Always use underscores in html ids

Plus some other shifting around

bookwyrm/templates/snippets/status/headers/reading.html

@@ -0,0 +1,9 @@
+{% spaceless %}
+{% load i18n %}
+{% load utilities %}
+
+{% with book=status.mention_books.first %}
+{% blocktrans with book_path=book.remote_id book=book|book_title %}started reading <a href="{{ book_path }}">{{ book }}</a>{% endblocktrans %}
+{% endwith %}
+
+{% endspaceless %}