Show plugin name in document title

I think this is the most efficient way, so that the name only get's set when we fetch the plugin, and only changed back when the page is updated. Which, since it's React.js, shouldn't happen unless we move to a new page. 
nit: You can make this function parameterless, so as to remove the duplication of code of `this.state.name + " - Vim Awesome"`.