Untracked: Add travis integration.
Issue #2351729: Import Drupal 8 plugin and utility components.
Issue #2351729: Add ServiceProvider plugin type; fix path.
Issue #2351729: Add render_cache ServiceProviderInterface and sample.
Issue #2351729: Add CToolsPluginDiscovery class.
Issue #2351729: Add custom PluginManagerBase to be able to support PHP 5.3.

5.3 has no traits.
Issue #2351729: Add a generic default plugin manager.