Added UNSAFE_ prefix to deprecated lifecycle methods to avoid warning…

…s in React 16.9

version update

Merge pull request akiran#1272 from randallreedjr/before-change-curre…

…nt-slide

Before change current slide

Merge pull request akiran#1303 from YossOviedo/edit-readme-npm-save

Update README.md

Fix contributors link

updated readme

release 0.19

Version update with bug fixes

Merge pull request akiran#991 from akiran/dev

modified issue template to add demo playground

Release a new version