Theme gets always overwritten by 'default'

[ReneS1991]

Currently the index.js says the default theme should be 'default'. However, this default always overwrites the provided 'theme' you actually want.

It currently says the following:
var opts = defaults({ theme: 'default' }, options);

However, since we want to use our own theme, it should be the other way around otherwise it gets always overwritten by 'default':

var opts = defaults(options, { theme: 'default' });

Is there any specific reason why you set it explicitly to 'default'? If not, can you please provide the fix so it only falls back to the 'default' when there is no theme provided?