Add networking guide link for README
Add networking guide link for README

1. What is the problem
README now does not have networking network guide link.

2. What is the solution to the problem
Add the network guide link to the README

3. What the features need to be implemented to the Tricircle
No new features

Change-Id: I096db397a0c0de1cae6989398d1299eda85297be

openstack/tricircle,stackforge/tricircle,stackforge/tricircle,openstack/tricircle