Update Readme with get_tokens.py usage details

Started adding instructions for using get_tokens.py and Postman.

Author: ic-dev21

doc/Readme.md

@@ -0,0 +1,14 @@
+# Using get_tokens.py
+This python script will let you use it to log in to your Hilo account.
+
+From there, you will be asked to copy the full HA redirect(callback) URL and go back to your python script and press enter.
+
+Negotiation will take place and you will receive three distinct tokens:
+- Your access token
+- Your devicehub token
+- Your challengehub token
+
+Take care not to share your tokens as they are not encrypted and contain personally identifiable information.
+
+# Using Postman to send payloads to devicehub or challengehub
+## Prerequisite: you need to have your tokens on hand, they are relatively short lived so once you have them, get to connecting!