Fix regression introduced by #68

[wol-soft]

Validators which render a separate method and are transferred to a parent schema will render the method to the origin schema. Consequently, a call to the validator in the parent schema will cause a "call to undefined method" error. To fix the issue the validator scope gets updated at render time to make sure the method is rendered to the correct class.

[coveralls]

Pull Request Test Coverage Report for Build 4574843470

• 6 of 6 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 98.722%

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Totals
Change from base Build 4564521612:	0.002%
Covered Lines:	2781
Relevant Lines:	2817

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💛 - Coveralls