Add ability to parse presanitized text

[scgodbold]

This is in reference to #23 I opened earlier this week. I had some free time and figured I would take a stab at it. It attempts to add the ability to parse pre-sanitized input such as what terraform show provides. This helps enable use in automation as it is best to store your plan objects to assure a consistent apply occurs.

The idea being that passing a --clean flag to the parser tells it that only resource changes will be listed. Doing this there is no need to substring the plan to extract the changing resources.

[coveralls]

Pull Request Test Coverage Report for Build 112

• 8 of 8 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 103:	0.0%
Covered Lines:	171
Relevant Lines:	171

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💛 - Coveralls

[Druotic]

Thanks for the contribution @scgodbold! Overall, this looks great to me and your use-case sounds like a valid case to me. Just a minor comment on the test helpers. I'll add a couple of other reviewers so we can get this merged soon.