Fix the travis CI build [hack]

The travisCI build is breaking because the tests are being done against an old version of hiera-eyaml (1.3.4) that is references in the Gemfile.lock.

The root problem is that the Gemfile contains a dependency on hiera-eyaml-plaintext. This is used to test a whole bunch of the plugin features, verifying that the plugin integration is working. However, it depends on hiera-eyaml and by pulling in a version of the gem we end up running our tests against the gem instead of the source code in the project (this is bad).

The short term solution is to hack the Gemfile.lock so that hiera-eyaml isn't included. Longer term solutions might be to remove the dependency for the plaintext gem or require the plaintext gem via the `:github:` provider.