nmbug-status: Adjust headers to start with h1

We've been leading off with h2s since 3e5fb88f (contrib/nmbug: add
nmbug-status script, 2012-07-07), but the semantically-correct headers
are:

  <h1>{title}</h1>
  ...
  <h2>Views</h2>
  ...
  <h3>View 1</h3>
  ...
  <h3>View 2</h3>
  ...

We can always add additional CSS if the default h1 formatting is too
intense.