Added ctx parameter to Sign and Verify interfaces to allow context pa…

[khalkie]

…ssing in the case of remote calls to sign/verify an envelope (i.e. a KMS call)

[coveralls]

Pull Request Test Coverage Report for Build 4145744285

• 6 of 6 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 91.632%

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Totals
Change from base Build 3856310937:	0.0%
Covered Lines:	219
Relevant Lines:	239

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💛 - Coveralls

[adityasaky]

@khalkie could you squash your commits? They all have the same message. Thanks!

[adityasaky]

Also, we should quickly check who we'd break with this change.

[khalkie]

Also, we should quickly check who we'd break with this change.

Thanks! I've squashed the commits but I'm unsure how to check what it has broken. Do you do that, or can you show me how to do it?

[khalkie]

Please advise next steps

[adityasaky]

Thanks for the patch, @khalkie! We've cut a release of go-sslib with this included (s/o @shibumi) and working on updating in-toto-golang to support it as well.