Partially restore styling to links in footer and make them more accessible to screenreaders

As part of the move from Suzy to Bootstrap, most styling was removed.  This commit:
* restores icon images to links in footer
* adds img tags so that alt attributes can be added for screenreaders
* fixes minor indentation and capitalization nits in the primary layout file
Merge pull request #63 from eleather/master

Partially restore styling to links in footer and make them more accessible to screenreaders