v2.7.1

This release adds the following changes on top of https://github.com/emilsjolander/StickyListHeaders/releases/tag/2.7.0:

• Fix insufficient instance state handling that causes crashes on O: emilsjolander#477
• Support for long click listeners on headers: emilsjolander#347
• Prevent possible race condition in adapter: 7c5d2e8