fix(README): updates proxy information

README.md

@@ -10,6 +10,11 @@ By the end of this lab you'll be able to message each other in an end to end enc
 
 You will need to install a few things to get started, buckle up.
 
+Firstly you need to export some environment variables in your working terminal to be able to talk to the outside world using the school's proxy:
+```
+export https_proxy=http://proxy.polytech-lille.fr:3128
+```
+
 ### The virtualenv
 
 Since Ansible is written in python and we don't want to install it in the system, you will need to create a virtual environment. These are used to have your python stuff installed, without making them available system-wide, we are doing this to avoid polluting your lab machine with things that won't be used after today.