Adding back social widgets plus minor formatting tweaks.

Added social sharing widgets back to post and page layouts. Tweaked archive archive_post include so that all items are grouped in container, rather than many. Small adjustment to dt element to allow projects with longer names to appear cleanly. Minor LinkedIn link change: the /in path in the URL doesn't seem to be a standard one, so I snipped it.

The theme is great overall! Thanks for making it.

![comments social](https://f.cloud.github.com/assets/3002110/147686/cf315cc8-74c7-11e2-9dc8-53631aecdfde.png)
![archives](https://f.cloud.github.com/assets/3002110/147687/cf2a67e2-74c7-11e2-838c-e909875539a2.png)