Add a multiple option to {{md-select}}

[Gorzas]

I've seen that MaterializeCSS has a selector with multiple property but we don't allow it in {{md-select}}:

I think we can added. We have two options:

• adding the property to the component {{md-select}}.
• creating a new component called {{md-select-multiple}}.

What do you think? I'm going to send a PR with the changes as soon as I can.

[mike-north]

I would love this to be one {{md-select}} component, built with the intent of refactoring away the materialize javascript away and replacing it with some more SPA-friendly implementation