Headings are not hierarchical

[sukiletxe]

When reading the spec, I notice that the table of contents is fine, but all headings are h1. This makes navigation harder for people who use them (blind people for example), as we can't skip to the next section without round trips to the TOC (I can only skip to the next heading, as they have the same level). Two possible solutions:

1. Put the headings of the spec in a hierarchical order (section 1 is h1, 1.1 is h2, etc.); or
2. Postprocess the code of epmarkup to change the heading levels and make them hierarchical, as it's already done in the TOC.

Of course, the end result will be the same.