Feature/config

[miljanic]

Add possibility for user to define whether he wants an object or associative array returned from all api methods.
Defaults to current value false and returns object

Also lint all files.

[vluzrmos]

You only need to change 3 files: readme.md, config/slack-api.php and SlackApi/SlackApi.php.

[vluzrmos]

And thank you for the contribution!

[miljanic]

@vluzrmos Not sure what you meant by only need to change 3 files? Should I undo the linting? Should I open another PR to lint all the files to some standard or you want them left untouched?
It's not a problem, I'm just not sure what did you mean exactly.
Thanks for response!