Add config for custom logout_path

[Trojan295]

• improvement for #30 and #36. Allow to define a custom logout_path and redirect_after_logout_uri.
• add CI envs for Kong 0.11, 0.12 and 0.13.
• make it easier to run the CI job locally

[coveralls]

Pull Request Test Coverage Report for Build 76

• 0 of 0 (NaN%) changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+40.6%) to 95.902%

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Totals
Change from base Build 67:	40.6%
Covered Lines:	117
Relevant Lines:	122

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💛 - Coveralls