Bump up to 4.0.1

Create CODE_OF_CONDUCT.md (#186)

Update CHANGELOG.md

2.3.0 (#151)

* update copyrights

* update gradle wrapper

* update sdk version

* update bintray tool

* update android tools

* update support library

update changelog

updated demo

bump up 2.2.5

update 2.2.4

bug fix

add interpolators