Make hard tabs align to columns.
Add editor component resize spec
Add the simplest resize fix that will work.
Move scroll view measurements to componentWillUpdate
Don't perform an update in response scroll view dimension changes

We always measure the scroll view in the ::componentWillUpdate hook, so
performing *another* update in response to the measurement causes an
invariant violation in react. Whenever we are measuring, we are always
already updating.
added delete to end of line
deleting only selection if selection is not empty
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