Update

* Fix bugs
- https://github.com/designwall/dw-timeline/issues/5
- https://github.com/designwall/dw-timeline/issues/7
- https://github.com/designwall/dw-timeline/issues/8
- https://github.com/designwall/dw-timeline/issues/10
* Customizer
- New:  Custom header mask
- New: Custom "get start button"