[FEAT fetch] use ember-fetch instead of jQuery

[NullVoxPopuli]

Continuation of #5386

just trying to fix some tests.

@tchak I can point this at your branch as well if you want

/cc @runspired

[runspired]

@NullVoxPopuli I'd open a PR to his branch as well

[NullVoxPopuli]

tchak#2

[NullVoxPopuli]

I think I fixed all the tests (at least locally).
I think there should probably be a good amount of tests for fetch, which don't exist yet.
also, with ember fetch, there is this function: mungOptionsForFetch

[runspired]

@NullVoxPopuli failing linting atm

[NullVoxPopuli]

Thanks! Updated

[tchak]

Thanks!

[NullVoxPopuli]

closed, cause this was merged into @tchak 's branch :)

#5386