Special Handling for Workflowy: Part 3

Please see [Other Workflowy Related Issues](https://github.com/tuvistavie/atomic-chrome/issues?q=workflowy)
## Description of Problem

In Workflowy's editor for notes it wraps links, bold, italics and underline.
- **Links** - Links are like this `[SITE]`... those links then get converted to text in Atomic Chrome. They then return and get wrapped again... and so on and so on.
- **Formatting** - Bold is like this ``, while italics use `contentItalics` and underline uses `contentUnderline`

Multiple formats are delimited with spaces in the `class` attribute, e.g., `class="contentItalic contentUnderline"` (as you would expect from CSS)
## Solutions

All of these tags should be removed on extraction to Atom.

I'm not sure this is specific for Workflowy. Any app that loads the contentEditable with HTML should have it expunged when it's moved to Atom, I think.