writing index, initial styles for abridged homepage writing archive

- Limit to 3 writing articles in the home index
- Added writing index page (same code as former home index)
- New `archive-link` style
- Fixed HTML background color for relatively tall screens (and short
content)
- Fixed margins for `site-nav` at intermediate viewport width
responsive `archive-link` styles for big screens

- `archive-link` now behaves like the other list items in the
`excerpt-index`
- Added comments to clarify CSS choices
- Transform property for archive-link ellipsis instead of conventional
link hover
pubdate is deprecated

source: http://microformats.org/wiki/html5
fixes for .site-nav width, top nav height
overflow and max-width `.excerpt-index` fixes

- "overflow: hidden" in place of "overflow: auto" (gets rid of
scrollbars in all cases)
- "max-width: 66em" broke the grid margins at >80em widths (outdated
CSS rule, I believe)
additional height for .excerpt items

The layout broke in Firefox and was threatening to break in other
browsers.
banner and nav padding fixes
experimental: ellipsis replaced with CSS-generated element
padding and margin fixes for ellipsis link
toning down the scaling of the ellipsis
more margin and padding fixes for the ellipsis
Merge branch 'ellipsis-animation-experiment' into home-index
Merge pull request #44 from opattison/home-index

Home index