Organize DisplayBufferMarker into sections. Add docs from Marker
Add DisplayBufferMarker::getInvalidationStrategy
Deprecate s|getAttributes for s|getProperties
DisplayBufferMarker::matchesAttributes -> ::matchesProperties
Shore up the docs around marker creation and invalidation
Rename DisplayBufferMarker -> Marker

Gnar!! :sunglasses:
Move buffer-display-marker -> marker
Upgrade text-buffer to have a private marker
Fix reference to display-buffer-marker
displayBufferMarker -> marker
Fix specs
Merge pull request #3569 from atom/bo-proper-doc-marker

Rename DisplayBufferMarker to Marker