Add grunt task runner for easier spec editing

Run `grunt edit` to get going.
Not sure if we really want to run bikeshed update every time.
Add absolute reference to fxtf default.css
Fix h4 headings
Check-in Overview.html made with updated bikeshed (not FXTF abstract)
Use standard note formatting
Fix formatting of switch lists
Replace some tabs
Fix todo colours
Mark reaching the end section as informative
Fix broken link
Close open div
Fix a space
Fix formatting of todo spans
Fix a list that should be unordered