Changed "book(s)" to "guide(s)" throughout.

NOTE: No change: the two following lines have links with "book(s)" embedded in them.
Line no.	issue
12		[/**books**/volunteer.yml](https://github.com/civicrm/civicrm-docs/blob/master/**books**/volunteer.yml)
101		Go to the [**books** configuration within our publishing system](https://github.com/civicrm/civicrm-docs/tree/master/**books**)

Changes include "guide book(s)" to "guide(s)" in par. 3 and 4 (lines 8, 10).

In second paragraph remove space between "overview] (https" to read "overview](https:" so that URL does not appear adjacent to "basic overview".

Identify two environments:  Docker for Windows / Mac / Linux and Legacy
OS (Windows 7, 8.1, 10 Home Premium).  Provide docker run commeands for
each environment.

Close #184

Close #86

Nice documentation :) I didn't realise it existed :)

This book isn't published yet, but I want to get this page up
and running. Will uncomment when CiviVolunteer books is up.