embedding content a markdown file

Based on issue #14 - many thanks to @lorenaSalome

To include images, gifs, or other files in the reflections or score markdown:

1. add the image/other files to the folder '/extensions' (create it if it doesn't yet exist).

2. Tell git to track the new image

git add /extensions/nameOfImageFile.png

3. in the markdown file (i.e. score.md), embed the image using relative path syntax:

![image name or some text or whatever](extensions/nameOfImageFile.png)

For reference, this github user demonstrates in detail:

https://github.com/mark-anders/relative-image-url

unsupported media types

So far we have found that video files cannot be embedded into github-flavoured markdown. It's possible that audio files can't be either. Best bet is to check how your score.md behaves on the web by going to your repository's url on github.com and clicking on 'score.md'