address CSSLint warnings about headings

[Rob Friesel]

CSSLint says:

26 | Heading (h*) has already been defined.
21 | Heading (h*) should not be qualified.
1 | You have 8 h1s, 7 h2s, 7 h3s, 4 h4s, 4 h5s, 2 h6s defined in this stylesheet.

analysis of headings in the mark-up

• h1 used...:
  ** blog title in #masthead
  ** used for page headings (404, category pages, tag pages, etc.)
• h2 used...:
  ** blog slugline in #masthead
  ** individual post titles
  ** also used
  ** 'about author' section for post footer
• h3 used...:
  ** #comments-title
  ** widget headings in main aside sidebar
  ** ...known to be used in some posts (for sub-headings)

plan:

• at a minimum: unify style declarations (one declaration for each...)
• re-factor usage w/in the php generating the mark-up (?)

[Rob Friesel]

added in 3f95533