chore(travis): make docs generate on the travis leader

The leader tries to push the API docs to docs.angulardart.org, and as
such needs to have the docs built.
Revert "refactor: remove unused import clauses"

This reverts commit 7c2846e34b8a9ed119ed05a4702cb02f8c97dd6c.
feature(directive_injector): add View to DirectiveInjector

Some directives require access to the current view. Add the view field to the DirectiveInjector class, so it can be injected.
feat(components): add support for multiple insertion points for transcluding components

Add implementations of the light dom and the content tag to support multiple insertion points for transcluding components.

Closes #1290
feat(urls): support relative CSS / template URLs in components

Example:
When defining a component called 'foo' in file
'/myproject/has/many/folders/foo.dart', prior to the change you would
do so thusly:
@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:
@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 "ON" state, but may be turned off using the
added ResourceResolverConfig class.  This class is added for backwards
compatibility in case users are already using relative urls from the root,
or other strange urls that may break when relative url rewriting is turned on.
i.e.:
'foo.html' really should reference '<root>/foo.html'
This feature will eventually be deprecated in a future release.

through the addition
of the ResourceResolverConfig class.  We do this for backwards compatibility
in case users are already using relative urls from the root, i.e.:

'foo.html' should really reference '<root>/foo.html'.

Or other strange url definitions.  Eventually the backwards compatibility
feature will be defaulted to an "on" state.

To turn the feature off using the Config, bind a new ResourceResolverConfig
in your module:

module.bind(ResourceResolverConfig, toValue:
	new ResourceResolverConfig(useRelativeUrls: false));

*Testing*:
- e2e transformer tests can now be done on the sample application found
  in the test_transformers folder