Incorrect property name case of YAML serialized results

[BernieWhite]

Description of the issue

Results for Invoke-PSRule with -OutputFormat Yaml should produce results formatted with lower camel case property names.

To Reproduce

Steps to reproduce the issue:

Get-Content docs/scenarios/kubernetes-resources/resources.yaml -Raw | Invoke-PSRule -Path docs/scenarios/kubernetes-resources -Format Yaml -Option docs/scenarios/kubernetes-resources/PSRule.yaml -Outcome Fail -OutputFormat Yaml

- RuleId: kubernetes.Rule.ps1/deployment.HasMinimumReplicas
  RuleName: deployment.HasMinimumReplicas
- RuleId: kubernetes.Rule.ps1/deployment.NotLatestImage
  RuleName: deployment.NotLatestImage
- RuleId: kubernetes.Rule.ps1/deployment.ResourcesSet
  RuleName: deployment.ResourcesSet
- RuleId: kubernetes.Rule.ps1/metadata.Name
  RuleName: metadata.Name
- RuleId: kubernetes.Rule.ps1/metadata.Version
  RuleName: metadata.Version
- RuleId: kubernetes.Rule.ps1/metadata.Component
  RuleName: metadata.Component
- RuleId: kubernetes.Rule.ps1/metadata.Version
  RuleName: metadata.Version

Expected behaviour

Serialized YAML results should use lower camel casing for property names.

Module in use and version:

• Module: PSRule
• Version: 0.4.0-B190320

Captured output from $PSVersionTable:

Name                           Value
----                           -----
PSVersion                      5.1.17763.316
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.17763.316
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1