Basic working ui-tabs example

Works out of public directory
Add platform.js to javascript manifest

Put file in vendor directory and removed source map declaration
Moved polymer-ui-tabs to vendor folder

In preparation for next commit
Specify polymer-ui-tabs dependencies directly

In preparation of next commit
Added working element_include_tag
Change name of import tag to html_import_tag
Removed unnecessary include in ApplicationHelper
Remove manual dependencies
WHY???????