feat: add title-bar-content and title-bar-transclude directives

These can be used to customize the title bar for different routes.
Merge branch 'master' of https://github.com/mvbschot/hands-on-angular-2 into title-bar-transclusion
Merge branch 'master' of https://github.com/mvbschot/hands-on-angular-2 into title-bar-transclusion
Merge branch 'master' of https://github.com/mvbschot/hands-on-angular-2 into title-bar-transclusion

Conflicts:
	src/directives/index.js
	src/index.html
refactor: rename title-bar-transclude to title-bar-view-port
Merge pull request #1 from mvbschot/title-bar-transclusion

Title bar transclusion