Update meta.hbs to fix Twitter Cards

To get a basic summary card from Twitter they REQUIRE the meta tags "twitter:card", "twitter:title" and "twitter:description". I've added "twitter:card" and "twitter:description".

Having said that Twitter Cards will only work for your index page. The meta.hbs file has to be hooked into every post for twitter cards to properly work. 

E.g If I tweet the link www.mikeyjck.com it will have a Twitter Card however www.mikeyjck.com/up-running/ will not.