Bold italic text is not rendered correctly

[marklcrowe]

Test in markdown (md or Rmd) files formatted as bold italic only displays as italic in the generated webpage.

The HTML code is generated correctly "\<b>\<i>TEXT\<\/i>\<\/b>" but something in the style settings seems to be overriding the correct display.

Test case: add the following as a test episode:

---
title: "Test"
teaching: 5
exercises: 5
---

:::::::::::::::: questions
- None 
:::::::::::::::

:::::::::::::::: objectives
- None
:::::::::::::::: 

### Bold italic testing
**This is bold**. *This is italic*. ***This should be bold italic***

:::::::::::::::: keypoints
- None
:::::::::::::::: 

[zkamvar]

Hi Mark,

I have confirmed that this indeed is a bug and you are correct that it is something that's specific to how the CSS is dispatched.

I don't have much expertise in fonts, but I've created a pull request in #91 that might fix the issue.