Drop support for Node.js 4 and below

[Turbo87]

Unblocks several dependency updates. This is a breaking change and requires a major version bump! (or a minor bump in this case as we're still pre-1.0)

[rwjblue]

Can you also remove the custom resolutions and unlock the ember-data version in package.json?

[Turbo87]

unlock the ember-data version in package.json?

what do you mean by that? ember-source and ember-cli are also at v3.1.x currently and updating them to something else seems not directly related to dropping Node 4 support 🤔

[rwjblue]

I was referring to the resolutions field in package.json (where I had added custom resolution overrides to avoid various Node 4 breaking packages) and the fact that I was forced to pin ember-data to a specific 2.18 release because later patch releases broke node 4 compatibility. Seems _OK_ if you really don’t want to update them here, but they were only pinned due to Node 4 issues so it seemed reasonable to undo in a Node 4 dropping PR to me...

[Turbo87]

@rwjblue I've removed the resolutions, but ember-data is currently pinned to v3.1.1, which seemed okay to me:

ember-test-helpers/package.json

Line 51 in 03373db

"ember-data": "3.1.1",

[rwjblue]

Ya, seems ok, I’m just saying that the reason I pinned it was due to node 4 issues. I’ll fix it in a follow up.