Add public initializer for TMAnimation

[netspencer]

From the Swift Documentation:

Default Memberwise Initializers for Structure Types

The default memberwise initializer for a structure type is considered private if any of the structure’s stored properties are private. Otherwise, the initializer has an access level of internal.

As with the default initializer above, if you want a public structure type to be initializable with a memberwise initializer when used in another module, you must provide a public memberwise initializer yourself as part of the type’s definition.

This makes it possible to create an instance of TMAnimation from outside the module.

In my app, I am creating a TMBar outside of a TabmanViewController, and in order to call bar.update(for:capacity:direction:animation:), I ned to be able to create an instance of TMAnimation, which is only possible if TMAnimation has a public initializer.

[msaps]

@netspencer ah yeah good catch, thanks! 😄

[msaps]

Available in Tabman 2.1.0 🎉