Streams receiving peer reset clear pending send (#238)

Because streams that were being peer reset were not clearing pending
send frames / buffered_send_data, they were not being counted towards
the concurrency limit.

src/proto/streams/send.rs

@@ -283,6 +283,15 @@ impl Send {
         Ok(())
     }
 
+    pub fn recv_reset<B>(
+        &mut self,
+        buffer: &mut Buffer<Frame<B>>,
+        stream: &mut store::Ptr
+    ) {
+        // Clear all pending outbound frames
+        self.prioritize.clear_queue(buffer, stream);
+    }
+
     pub fn recv_err<B>(
         &mut self,
         buffer: &mut Buffer<Frame<B>>,