Change syntax from @inject @Named('foo') to @Inject(name: 'foo')

First of all, this is a _totally_ stylistic change, and a breaking one at that. I just think the latter looks a little terser, especially because the form.

``` dart
const foo = const Foo();
```

lends itself very well to optional named parameter. Named parameters are already used in a number of projects, e.g. polymer.

I have a pull request for your consideration.
