2d animation package throws errors when installed through package manager.
Steps to reproduce:
1) Create new project
2) Window > Package Manager
3) Install the latest version(1.0.16) of 2d animation

Actual result: Namespace error appear in the console.

Occurs on : 2018.3.0a6, 2018.3.0a5, 2018.3.0a4

Working fine on : 2018.3.0a3

Packman version: 2.0.0

Environment: Both Windows and Mac

Stack trace:
C:\Users\gs1801\AppData\Local\Unity\cache\packages\packages.unity.com\com.unity.2d.animation@1.0.16-preview\Runtime\SpriteSkin.cs(206,104): error CS0103: The name 'VertexAttribute' does not exist in the current context