more analytics events on various buttons

[cboettig]

• Distinguish footer and lab-notebook.html based links to twitter, mendeley, github(?)
• generic event for history button
• RDF button shouldn't be "outbound link" category, maybe "download" category pointless
• vita button label something other than "PDF"? (but lose stats on changing..) nope.

Analytics for internal links?

• generic events for next/prev?  Nope, just see flow
• other key internal links? Nope, see site flow

[cboettig]

More broadly, complete data on all outgoing links would be useful (e.g. what citations get the most clicks, etc). Would still want categories to distinguish by type of outgoing link. Need a comprehensive approach here. Would require modifications to the markdown renderer, or possibly a javascript post-processing of links instead.

Internal links are covered with built in GA tools: flow diagrams, etc.

[cboettig]

• Add tracking for knitcitations links?
• Add tracking for arXiv, code, and Dryad links in Vita