ember-element-helper required in alpha

[cloke]

We just updated to v.17 alpha. It looks like there is a hard dependency on ember-element-helper because of the divider component. I was going to PR adding the dependency, but made me think, since there is only one component using this add-on would the direction be to add the package or modify divider component to use a different approach.

[josemarluedke]

Feel free to open a PR changing the approach, but one restriction I have is that it needs to work in FastBoot, so the modifier won't do it.