#57 Adding support for terraform validate command.

[kevbite]

This adds support for the terraform validate command (#57 - https://www.terraform.io/docs/commands/validate.html).

Motivation and Context

We wanted this feature so that we can do basic validation of our terraform scripts in our CI pipeline without having to do StartProcess.

How Has This Been Tested?

Unit tests

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[nils-a]

LGTM!

[nils-a]

@kevbite your changes have been merged, thanks for your contribution 👍