Support linking to models via `ui-sref="model"`

Rather than encoding the state names and parameters in different modules,
this allows a default implementation (state name is `<modelType>.show`,
state params are `{<modelType>Id: <model>.id}`) and the ability to
override at the model level. Because models are typically defined in the
same module as their states, this reflects the structure of the app better
and allows more localized management of a given module.

```html
<a ng-href="/accounts/{{account.id}}"></a>
<a ui-sref="account.show({accountId:account.id})"></a>
<a ui-sref="account"></a>
```

These are generally equivalent, but the first becomes out of date if
the state's url format changes, the second becomes out of date if the
state's name (might happen if heirarchy needs to change) or parameters
change.
skeleton accounts
Use `Controller as x` syntax

By using controller as x syntax, it becomes easier to reason about
which part of the app is responsible for which pieces of scope when
nesting controllers (as we begin doing soon for things like stories
within accounts). It also removes the temptation to communicate
between controllers using $scope, which always leads to heartache.
Use semantic markup, break module concerns out

* Use the semantic markup patterns agreed upon in chat room
* Break module-specific styles into module specific stylesheets
* Use soft-dependencies on external modules for rendering (see below)
* remove crufty styles we are no longer using

If styles are split by the module using them, it becomes important
to ensure that the stories module is responsible for rendering stories.
Using directives can accomplish this pretty easily, and declaratively.

By declaring a directive with an isolate scope using a template, we're
effectively creating a clean environment in which the module can render
however it needs to. The accounts module doesn't need to be aware of what
methods the stories module adds to story objects, because it (very likely)
never needs to call them.
Merge pull request #30 from PRX/feat/producer

Feat/producer