Add support for PE RBAC token use with PuppetDB

[JohnLyman]

Overview

This pull request adds the ability to use a PE RBAC token with PuppetDB.

Closes #156

Checklist

• Make sure that all of the tests pass, and fix any that don't. Just run rake in your checkout directory, or review the CI job triggered whenever you push to a pull request.
• Make sure that there is 100% test coverage by running rake coverage:spec or ignoring untestable sections of code with # :nocov comments. If you need help getting to 100% coverage please ask; however, don't just submit code with no tests.
• If you have added a new command line option, we would greatly appreciate a corresponding integration test that exercises it from start to finish. This is optional but recommended.
• If you have added any new gem dependencies, make sure those gems are licensed under the MIT or Apache 2.0 license. We cannot add any dependencies on gems licensed under GPL.
• If you have added any new gem dependencies, make sure you've checked in a copy of the .gem file into the vendor/cache directory.

[kpaulisse]

Hey @JohnLyman !

Thanks for the contribution of PE token authentication for PuppetDB. The code looks good to me, so I'm going to run this through our normal release process (a couple days of internal testing in our Puppet install within GitHub) and then push it out as a new minor release.

🎉

[JohnLyman]

Great, thanks!

[kpaulisse]

Will merge as part of #172. Thank you for your contribution!

[kpaulisse]

Hey @JohnLyman - this is all merged, thanks!

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