Event errors and invisible bug

[svrooij]

Description

This PR fixes the #127 bug, by emitting an event if the subscription is unsuccessful. It also fixes #125 by better parsing zone groups.

Your checklist for this pull request

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• [x] Make sure you are requesting to pull a topic/feature/bugfix branch (right side). Don't request your master!
• [x] Make sure you are making a pull request against the beta branch (left side). Also you should start your branch off svrooij/node-sonos-ts/beta.
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• [x] Check you add tests for added code.

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[coveralls]

Pull Request Test Coverage Report for Build 551636531

• 60 of 66 (90.91%) changed or added relevant lines in 6 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 78.442%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/sonos-device.ts	14	15	93.33%
src/services/base-service.ts	14	16	87.5%
src/sonos-event-listener.ts	20	23	86.96%
<!--	Total:	60	66	90.91%	-->

Files with Coverage Reduction	New Missed Lines	%
src/services/base-service.ts	2	90.83%
<!--	Total:	2		-->

Totals
Change from base Build 504514344:	-0.02%
Covered Lines:	1454
Relevant Lines:	1856

---

💛 - Coveralls

[github-actions[bot]]

:tada: This PR is included in version 2.4.0-beta.4 :tada:

The release is available on:

• npm package (@beta dist-tag)
• GitHub release

Your semantic-release bot :package::rocket:

[github-actions[bot]]

:tada: This PR is included in version 2.4.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: