Math expressions not rendered in account overview

### Steps to reproduce
1. Write an annotation containing some math.
2. Go to hypothes.is/users/your_account
3. Find the annotation.

### Expected behaviour
Math expressions should be rendered similarly to how they are rendered inline with the website, because otherwise its not readable.

Sometimes its indeed handy that it doesn't get rendered because then one can copy the raw code but imo this should be rather implemented as an option into the Share button a la "copy raw text" which copies the raw Markdown code.

### Actual behaviour
Math expressions don't get rendered.


### Browser/system information
Firefox 58.0.1, macOS 10.13.3