Run accessibility test on Assist

[billymeinke]

Create accessibility plan to tackle this.

[billymeinke]

Most of the issues are with images that do not include alt text, but let's chat about this @fjumawan. Here's a start: http://wave.webaim.org/report#/assist.coe.hawaii.edu

[billymeinke]

After a quick audit, some things to fix:

• alt text for all images
• apply form control label to search bar (*may not apply since it is a 'submit' button)
• form control labels for Hypothes.is sidebar (*unsure if this is possible or practical)