Lightened article background color.

- Article background color is now lighter than main background.
- Darkened article borders.
Gave masthead header an id and moved post date next to article head.

- Post titles and dates are now floated to the left and right respectively.
- Needed a bounding box for this and the header tag seemed most appropriate, but the masthead header styled header elements, so gave it an id (#masthead) to style instead.
- footer styling is unchanged but perhaps could use similar treatment (e.g. change #masthead to .masthead). Haven't needed to use another footer element yet.
Removed some meta tags leftover from the original file.

- Please don't hate me, SitePoint!