Updating for Guzzle streams and ring updatres

src/Pool.php

@@ -202,6 +202,11 @@ class Pool implements FutureInterface
         return $this->promise->then($onFulfilled, $onRejected, $onProgress);
     }
 
+    public function promise()
+    {
+        return $this->promise;
+    }
+
     private function coerceIterable($requests)
     {
         if ($requests instanceof \Iterator) {

src/Post/PostBody.php

@@ -212,11 +212,6 @@ class PostBody implements PostBodyInterface
         return false;
     }
 
-    public function flush()
-    {
-        return false;
-    }
-
     public function getMetadata($key = null)
     {
         return $key ? null : [];

tests/Post/PostBodyTest.php

@@ -167,7 +167,6 @@ class PostBodyTest extends \PHPUnit_Framework_TestCase
         $b = new PostBody();
         $this->assertEquals([], $b->getMetadata());
         $this->assertNull($b->getMetadata('foo'));
-        $this->assertFalse($b->flush());
     }
 
     public function testCreatesMultipartUploadWithMultiFields()