`showCredits` option entirely useless

[ilyvion]

Because of this logic

juxtapose/juxtapose/js/juxtapose.js

Lines 316 to 320 in c02a4c5

	if (this.imgBefore.credit || this.imgAfter.credit) {
	this.options.showCredits = true;
	} else {
	this.options.showCredits = false;
	}

which takes place after options are copied into this.options, it doesn't matter whether you pass showCredits in options or not, the only thing that matters is whether or not the images arguments have credit values.