Ability to open and close the component, change the background color through @ColorRes

Feature/community requests (#44)

* Add the ability to open/close the component, set color through resolved color

Exposed two new methods open/close and renamed the internal implementation toexpande/collapse respectivily, when the consumer opens or closes the component there is an exposed listener which'll trigger the respective callback to when the animation ends.

Fix: #35
See also: #41 (thanks @qijaz221 for your contribution)

* Update README with changelog

Remove blog comming soon  post since no artcile is going to be written 🔖

* Bump versions, set latest targetSdkVersion to 27

* update to implementation