Fix typo installation guide
Fix typo installation guide

1. What is the problem?
There were some typos in the title of installation guide that could
raises errors for documentation generator tools, e. g. sphinix.

2. What is the solution to the problem?
This change fixes the typo and format of the title and change the
plural for the environments referred in the installation guide.

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

Change-Id: Iac7d7cbb38c2af3541b2e6b860784cb52d8da7c0

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