Use EasyMDE for Preview

[tnyeanderson]

I took a look; we should definitely be using EasyMDE's preview functionality instead of Markdown-It. It supports checkboxes out of the box and prevents us from requiring another library. Here's what EasyMDE does not support that Markdown-It does:

• Emojis
• Blockquotes
• Images (displayed as block instead of inline, larger size
• Sub/Superscript
• Inserted text
• Marked text
• Footnotes
• Definition lists
• Custom Containers

Since we don't support these features anyway, making the switch makes sense.

Some useful notes for implementation:
Check if we are in preview mode: easyMDE.isPreviewActive();
Toggle preview mode: easyMDE.togglePreview()

This should be easy to implement. Then we can get rid of Markdown-It, AND have checkboxes available in preview mode :)

[korelstar]

This will be obsolete due to #331. Did you already did some implementation on this or can we safely close this issue, @tnyeanderson?

[tnyeanderson]

You're absolutely right. Closing.