remove unnecessary mentions of RSVP

[locks]

Closes #237.

@ppcano can you 👀?

[ppcano]

@locks

Ack "rsvp" guides/release/ still shows a few places where RSVP is referenced.

guides/release/configuring-ember/debugging.md
123:import RSVP from 'rsvp';

guides/release/contributing/repositories.md
58:* **rsvp.js** - Implementation of the of Promises/A+ spec used by Ember.
59:* [https://github.com/tildeio/rsvp.js](https://github.com/tildeio/rsvp.js)

guides/release/routing/asynchronous-routing.md
57:take a look at the readme for [RSVP](https://github.com/tildeio/rsvp.js),

guides/release/routing/specifying-a-routes-model.md
125:[RSVP.hash](https://www.emberjs.com/api/ember/release/classes/rsvp/methods/hash?anchor=hash).
131:import RSVP from 'rsvp';
214:import RSVP from 'rsvp';

In this Discuss post, there are two examples on how the RSVP.hash method could be refactored.

Thank you for working on this one.

[locks]

@ppcano I purposefully left those references because they seemed to make sense in context.

In the debugging section, it's talking about debugging RSVP promises.
Since RSVP has been recommended for a while and is still provided by default, it seems better to leave the prose in place.

The repositories reference was left for mostly the same reason. It is part of the default stack.
Another reasons for leaving it alone is that there is an (RFC for improving the Contributing guides)[https://github.com/emberjs/rfcs/pull/446].

I kept RSVP.hash because I think it is cleaner and less error prone than the refactorings.

I've removed the mention in the async routing guide!

[ppcano]

@locks As feedback, I would remove RSVP.hash but I see your point.

LGTM

[MelSumner]

👍