Cache selector results to improve performance

[kerrishotts]

For example (https://github.com/CeroyUno/JavaScriptView/blob/master/js/jsview.js#L46)

if(!$v.select('#' + obj)){
    ...
    $v.select('#' + obj).classList.add('JSVcontainerRight');
    $v.select('#' + obj).classList.add('JSVcontainerTransition');
    ...
}

This is inefficient, as the DOM is being queried each time. Better to do:

var objElement = $v.select('#' + obj);
if (objElement) {
    ...
    objElement.classList.add('JSVcontainerRight');
    objElement.classList.add('JSVcontainerTransition');
    ...
}

[JoseJPR]

We have made this change. :) But I think that we can improve this point.