Small corrections for Bin and Dynamic Pads code examples (#94)

* small changes to the code samples

* Correction based on review comments

Author: drewknab

basic_pipeline_extension/02_Bin.md

@@ -34,7 +34,7 @@ defmodule Basic.Bin do
     spec = [
       child(:input, %Basic.Elements.Source{location: options.input_filename})
       |> child(:ordering_buffer, Basic.Elements.OrderingBuffer)
-      |> to(:depayloader, %Basic.Elements.Depayloader{packets_per_frame: 4}) 
+      |> child(:depayloader, %Basic.Elements.Depayloader{packets_per_frame: 4}) 
       |> bin_output(:output)
     ]
 

basic_pipeline_extension/03_DynamicPads.md

@@ -42,7 +42,7 @@ The very first thing we need to do is to use the `def_input_pads` appropriately.
 ...
 def_input_pad :input, 
    demand_unit: :buffers, 
-   flow_control: :pull, 
+   flow_control: :manual, 
    availability: :on_request, 
    accepted_format: %Basic.Formats.Frame{encoding: :utf8}
 ...