Move the module reference to the top

Instead of having to scroll down to the bottom to read the module
reference, it'd be better to make it available for developers before
they get into the "how contribute section". This way, we can keep zaqar
and openstack sections grouped respectively.

Change-Id: I8c5e39e09352ba13b3fe2bf2d04a1dac93ac6509
Merge "Move the module reference to the top"