jeox: getters

[icmx]

There should be a getting logic like in original jQuery for some of methods, like this:

const example = $('.example'); // suppose it's a jeox instance

example.attr('type', 'text'); // -> set attribute 'type' to 'text' on each node; return chainable instance
example.attr('type'); // -> return attribute value like 'text' if there's only one node in instance or [ 'text', 'number', ...] if there's more

[icmx]

Closed due to #39.