Error on canary: `{{#with}}` is deprecated

[gitKrystan]

Hello there!

We are running into this deprecation on our canary builds:

Template Compiler Error (broccoli-persistent-filter:TemplateCompiler) in ember-elsewhere/templates/components/from-elsewhere.hbs

`{{#with}}` is deprecated. If you always want the block to render, replace `{{#with}}` with `{{#let}}`. If you want to conditionally render the block, use `{{#let}}` together with `{{#if}} instead. ('ember-elsewhere/templates/components/from-elsewhere.hbs' @ L6:C6) 

Looks like it comes from this template:

ember-elsewhere/addon/templates/components/from-elsewhere.hbs

Lines 6 to 8 in dadfa69

	{{#with active.lastObject.component as |c|}}
	{{component c}}
	{{/with}}

Happy to make a PR if you'd like. I don't know enough about ember-elsewhere to know if I should make the block render conditionally or if just replacing {{#with}} with {{#let}} would be appropriate. Thoughts?

[chancancode]

The deprecation for "property fallback" (i.e. use this.active.lastObject.component instead of active.lastObject.component) is about to land on canary as well

[cah-brian-gantzler]

this was fixed with #50