Changes for accessibility

[jhpyle]

trafficstars

Tasks that would improve WCAG compliance include:

• Issue #105 on keyboard navigation in multiple choice questions;
• Making sure tab order is sensible and all elements can be keyboard-driven;
• Finding an accessible Bootstrap 4 theme;
• Features for adding alt text to images.

[jhpyle]

#105 is closed now; tab order is cleaned up and all elements (to my knowledge) can be keyboard driven.