Add keyboard navigation between posts and pages

* Use jQuery and mousetrap
Add footer links to photography pages
Update content headings from h3s to h2s

* Content headers were directly beneath the main content title
* Legacy content was imported with wrong headers
Add subheadings to vulcano, saigon, harrogate
Add headings to cambodia, barcelona, borneo posts
Add headings to hoi an, honeymoon and hue