Add documentation for tags methods

Author: Einenlum

doc/README.md

@@ -19,6 +19,7 @@ APIs:
   * [Contents](repo/contents.md)
   * [Releases](repo/releases.md)
     * [Assets](repo/assets.md)
+  * [Tags](repo/tags.md)
   * [Deployments](repo/deployments.md)
 * [Users](users.md)
 * [Meta](meta.md)

doc/repo/tags.md

@@ -0,0 +1,8 @@
+## Repo / Tags API
+[Back to the "Repos API"](../repos.md) | [Back to the navigation](../README.md)
+
+### List all tags
+
+```php
+$tags = $client->api('repo')->tags('twbs', 'bootstrap');
+```