feat(urls): support relative CSS / template URLs in components

Example:
When defining a component in file `/myproject/has/many/folders/foo.dart`, prior to the change you would do so thusly:
```dart
@Component(
   selector: 'foo',
   templateUrl: '/myproject/has/many/folders/foo.html',
   cssUrl: '/myproject/has/many/folders/foo.css'
)
```

The above is still valid, but now can also be defined rather more succinctly as:
```dart
@Component(
   selector: 'foo',
   templateUrl: 'foo.html',
   cssUrl: 'foo.css'
)
```

A full table of what URLs will be changed/unchanged is below:

You Say:|Transformer replies:
------|------
`packages/foo/bar.html`|`packages/foo/bar.html`
`foo.html`|`packages/foo/bar.html`
`./foo.html`|`packages/foo/bar.html`
`/foo.html`|`/foo.html`
`http://google.com/foo.html`|`http://google.com/foo.html`

*Note  that as  shown any absolute paths you define will not be bothered by the transformer, so if you have a templateUrl living at `<root>/foo.html`, you can still reach it with `/foo.html`!

This feature is defaulted to an "off" state through the addition of the `ResourceResolverConfig` class.  To turn the feature on, bind a new `ResourceResolverConfig` in your module:

```dart
module.bind(ResourceResolverConfig, toValue:
	new ResourceResolverConfig(useRelativeUrls: true));
```

*Testing*:
- e2e transformer tests can now be done on the sample application found in the test_transformers folder
This creates a new variable.  You want to reassign to the uriMapper variable you already have.