v0.17.2

Fixed

• split_template/2 rendered a static ref or key as an attribute, and passed ref and key to a component as props. Vue reserves both and never renders them; now neither does the split, static or bound.
• A <select v-model> rendered no selected option, with a warning. Each <option> inside it now has a :model slot in its start tag, with the select's value and the option's own: its bound :value, its value attribute, or its text, so a renderer can mark the selected one, as Vue's server renderer does. The slot's new :option_value holds a bound :value.