Update to Swagger 1.2. Fixes #11, #8, #7.

Changes in this PR:

* Moved swagger-ui/dist out of this module and required as a module in `package.json`.
* Added `swaggerDistRoot` option so users of the API Explorer can override any part of the UI (styles, JS, HTML).
* Compatibility with Swagger 1.2 [spec](https://github.com/wordnik/swagger-spec/blob/master/versions/1.2.md) [transition guide](https://github.com/wordnik/swagger-spec/wiki/1.2-transition)
* Model schemas are now correctly populated.
* An `accessToken` can be provided via the header input.

When this is merged, it should be safe to remove `strong-remoting/ext/swagger`, the associated test, and `app.docs()`.