Footnote

<h3>Revised footnote-link Branch</h3>
+ css fix only
+ https://github.com/Connexions/oer.exports/blob/master/xsl/dbkplus.xsl#L421 (unable to resolve)

<h4>Testing</h4>
+ Biology: http://naginata.cnx.rice.edu:9090/content/col10001/latest/pdf
+ Physics: http://naginata.cnx.rice.edu:9090/content/col10003/latest/pdf
+ Sociology: http://naginata.cnx.rice.edu:9090/content/col10004/latest/pdf