add Apps endpoint delete /apps/installations/:installation_id:

Author: jamiehuson

lib/Github/Api/Apps.php

@@ -66,6 +66,18 @@ public function getInstallation($installation_id)
         return $this->get('/app/installations/'.rawurldecode($installation_id));
     }
 
+    /**
+     * Delete an installation of the application
+     *
+     * @link https://developer.github.com/v3/apps/#delete-an-installation
+     *
+     * @param $installation_id An integration installation id
+     */
+    public function removeInstallation($installation_id)
+    {
+        $this->delete('/app/installations/'.rawurldecode($installation_id));
+    }
+
     /**
      * List repositories that are accessible to the authenticated installation.
      *

test/Github/Tests/Api/AppTest.php

@@ -56,6 +56,20 @@ public function shouldGetInstallationForApplication()
         $this->assertEquals($result, $api->getInstallation('1234'));
     }
 
+    /**
+     * @test
+     */
+    public function shouldDeleteInstallationForApplication()
+    {
+        $id = 123;
+        $api = $this->getApiMock();
+        $api->expects($this->once())
+            ->method('delete')
+            ->with('/app/installations/'.$id);
+
+        $api->removeInstallation($id);
+    }
+
     /**
      * @test
      */