bug(ie): Object doesn't support property or method 'assign'

[prescottprue]

What is the current behavior?
Initialization fails when attempting to use v1.4.0 in Internet Explorer on Windows 10 (this was seen through a error log, not actually experienced)

The following error is displayed:

Object doesn't support property or method 'assign'

This is due to usage of Object.assign, which is not supported in IE.

What is the expected behavior?
Should work regardless of browser or operating system

Which versions of dependencies, and which browser and OS are affected by this issue?
OS: Windows 10
Browser: Internet Explorer 10