Fixed DeserializationException + improved unit testing

[93Omar]

Fixes #20

• Updated the SongResponse model
• Improved unit testing: added more tests (testing ArtistClient, SongClient, SearchClient and AnnotationClient)

There are a lot of changes but most of them are related to code indentation performed by CTRL + K, CTRL + D shortcut on Visual Studio so don't worry.
I added more tests in order to be sure I didn't break other functionalities. You can run them, if you want, after putting the API key in the App.config file.

[prajjwaldimri]

Can you set your indentation level to 2 spaces instead of 4? That's the convention I follow. Thanks :)

[93Omar]

@prajjwaldimri done.

[prajjwaldimri]

@OmarPani93 Should I merge this?

[93Omar]

@prajjwaldimri if you want you could merge it already.
I just want to run more tests, like fetching massive artist and song data, in order to find other problems, if there are. Anyway, yesterday I fetched like 2000 songs with the version you can see in this PR and everything was working.

[prajjwaldimri]

@OmarPani93 Alright. We'll merge it when you complete your tests.

[prajjwaldimri]

@OmarPani93 Any updates on the tests?

[93Omar]

Hi @prajjwaldimri, sorry for the delay. I have been busy recently. Hopefully I will do the tests in the next couple of weeks. Sorry again.

[prajjwaldimri]

Hey Omar. No worries. :) Looking forward to merging your changes in the repo.