Update 'README.md'

README.md

@@ -1,2 +1,16 @@
 # geocode_class
 
+**NOTE: There is a file missing (class/key.php)** 
+
+You will need to get your own Google API Key
+
+Change the **YOUR KEY HERE** with your key.
+
+Keep the key= part as it is required for the string.
+
+key.php
+```
+<?php
+	CONST API_KEY = 'key=YOUR KEY HERE';
+
+```