Update README.md

hw3/README.md

-# Homework 1. Introduction to Python and File I/O
+# Homework 3. Introduction to Python and File I/O
 This homework assignment is meant to be an introduction to Python programming and introduces some basic concepts of encoding and decoding. 
 
-Due Date: *Friday April 17, 2020 11:59 pm*
+Due Date: *Friday April 30, 2020 11:59 pm*
 
 ## Initial Setup
 These initial setup instructions assume you've done ``hw0``. Before you start an assingment you should sync your cloned repository with the online one: