Delete mailbox

[ghost]

Added "deleteMailbox" implementation. see #157

[felixhammerl]

Thanks for the submission! Before I merge this, could you...

• fix the linter errors,
• add a test,
• remove the async/await as it doesn't really make a lot of sense to await the result of the computation if we're going to re-throw the error anyway. Just return whatever Promise comes back from exec.

Cheers
Felix

[ghost]

i've pushed another commit, please tell me if another update is required :)

[smallbitt]

The npm is not updated.