update reveal.js framework to allow 'data-background'

[johnstantongeddes]

The revealjs framework needs to be updated to the newest version which allows setting custom color background or images using the 'data-background' argument. In addition, the "section" line of the "slide.html" template should be updated:

<section class='{{slide.class}}' data-state='{{slide.ds}}' id='{{slide.id}}' data-background='{{slide.background}}'> 

so that the data-background can be set within the index.Rmd file as such:

--- .background "#007777"

See this question on stackoverflow

Thanks for the great tool and quick help!

[jonathan-g]

You can do this yourself.

Edit libraries/frameworks/revealjs/layouts/slide.html and libraries/frameworks/revealjs/layouts/vertical.html and edit the html tags to look something like this:

```<section class='{{slide.class}}' data-state='{{slide.ds}}' id='{{slide.id}}' data-background='{{slide.bg}}' data-transition='{{slide.dt}}' background-transition='{{slide.bt}}'>```

Then you can specify a slide like

---  bg:#007777 dt:slide bt:fade

to set the background, data transition, and background data transition.