[Performance Platform] Add more repositories

- backdrop-collector-plugins
- backdrop-customer-satisfaction-collector
- backdrop-transactions-explorer-collector
- cheapseats: testing
- gapy: for Google Analytics
- ci-puppet: Puppet for the CI Jenkins
- release: managing our releases
- smokey: testing our apps on GOV.UK
- styleguides: how we code
Merge pull request #79 from alphagov/update-perfplat-team

[Performance Platform] Add more repositories