4.2.0

Use the passive option for scroll/resize event listeners

4.1.0

• Feature: Add individual offsetX / offsetY options #25

4.0.0

BREAKING:
Replaced onMaximized callback with new onFit callback on PositionObserver. See #20

3.0.0

BREAKING: Added specific browser support which wasn't noted before. Must support requestAnimationFrame MutationObserver, Map. 93% of global browser users support these including IE 11

2.2.0

Adds horiztonal scrolling support. Thanks @tholman!

2.1.1

• [feature]: PositionObserver: add onMaximized option
• [bug fix]: ElementObserver: allow onEnter to be called multiple times when onExit isn't provided
• [change]: UMD name is viewprt not Viewprt

2.0.0

• Added scroll direction detection ('down'/'up')
• API: callbacks now all contain a second param viewportState which is an object containing the viewport state at the time of the callback { width, height, y, yDirection }