(maint) Updating test/demo setup instructions for Pegasus
(maint) Updating test/demo setup instructions for Pegasus

Updated instructions for Pegasus in the "Setting up a test/demo environment" section.
Removed instruction to checkout the cthun-connector branch because master branch now
works, and cthun-connector branch is now outdated and will not work with Cthun.
Also added example .pegasus config file.

puppetlabs/pcp-broker,puppetlabs/pcp-broker,puppetlabs/pcp-broker