Use ::getMarker for fold decorations instead of new DisplayBufferMarker
Add startScreenRow and endScreenRow to DisplayBuffer::findMarkers
Add containedInScreenRange to DisplayBuffer::findMarkers
Add intersection support to DisplayBuffer::findMarkers
Move decoration Editor specs to DisplayBuffer
Decorations can now only be attached to markers.

The basics work. It will render them on the gutter.
Fix decoration specs to work with markers only
Make foldable decorations work again
Only render on updates
Add a spec for screen line changes
Rename bufferRowHasClass
Rename Selection(s)Component to Highlight(s)Component
Use decorations to render selections
No more typeless decorations

Now you can specify a list of types with your decoration.
Pass the decoration hash into the gutterComponent
Pass highlightDecorations into the HighlightsComponent
Remove Decorations object
Remove `getGutterDecorations()`
Remove `getSelectionScreenRanges()`
Make selection updating work properly