How to easing like specialEasing of jQuery animate?

[JarvisChao]

Your system information

• VelocityJS version: 2.0.6
• Browser: chrome
• Operating System: ios

Checklist

• Is this an issue with code?: [Yes]
• Is this an issue with documentation?: [Yes]
• Have you checked for updates?: [Yes]
• Have you checked for similar open issues?: [Yes]

Please describe your issue in as much detail as possible:

1. Is there any code that can achieve specialEasing like jQuery animate?
2. How to use relative position in v2.0.6? When I use '+=', it does not work properly.

thanks