Anonymous mixins don't include any defined properties.

[oatw]

Version
0.3.3

Describe the bug
Anonymous mixins don't include any defined properties.

To Reproduce
Steps to reproduce the behavior:

1. Define an anonymous mixin as the below code:

let toggleable = luda.mixin({
  toggleableCreate: function(){
    console.log('creating a instance.')
  },
  toggleableActivate: function(){
    console.log('activate a instance.')
  }  
})

2. Try getting all properties in the defined mixin:

// returns {}
toggleable.all()

Expected behavior
An object with all the defined properties should be returned.

What is Actually Happening
An object without any defined properties is returned.