[CHORE] Move ember-test-selectors from deps to devDeps

[bantic]

ember-test-selectors does not need to be a dependency.
It was moved from devDeps to deps in #537, which appears to have been unintentional.

As an aside, the data-test-* attrs that ember-table uses, e.g.

ember-table/addon/components/ember-table/component.js

Line 41 in 4cbaee8

'data-test-ember-table': true,

appear to leak out to consuming apps and should likely be removed.

[mixonic]

@bantic I think the idea might have been that [data-test- attributes are used in the page object of that PR which is in turn published for apps to use in test. Thus it was added as a dep so any consuming apps would strip the data-test-?

And additionally where data-test- is passed an an arg to components the author wanted those to be published as attributes?

I'm also unsure about if when data-test- selectors is installed in the app, but not in the addon's dependencies, if the stripping takes place on the addon/ folder. Often build-time addons only operate on an addon/ folder for the addon and the app/ tree for an app.

Anyway, I'm fine moving this to a dev dependency or not 😬 it is just a complex situation. Can you document in README what happens for an end-user in a) dev/test b) prod when they 1) don't use ember-test-selectors 2) do use ember-test-selectors?

[bantic]

@mixonic Ah, you're right. I thought I had tested this and confirmed that the data-test-* always leak to consumer apps but I just tried again and I see that they are stripped when running the consumer app in production environment. I had previously tried the published 2.0.0-beta.7 (not stripped) but the latest master (specifically, I pinned a local ember app to ember-table@aa56375ffae0d39325d8a) does strip them.
To add to the confusion, the beta.7 is not even the latest tag on npm, 2.0.0-beta.4 is, so in the consumer app if you ember install ember-table you get that older beta version.

Anyway, I think the right step here is to not move test-selectors but do add some docs that the page object exists: #715