Action view renderer & JSON support

[michelson]

This PR introduces a more Rails-ish way to render the views. using the ActionView renderer method from rails 5. Also this PR introduces the JSON support.

[coveralls]

Pull Request Test Coverage Report for Build 55

• 78 of 91 (85.71%) changed or added relevant lines in 11 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+10.3%) to 91.19%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib/policy_manager/exporter/view.rb	11	12	91.67%
lib/policy_manager/exporter/handler.rb	14	15	93.33%
lib/policy_manager/config.rb	0	2	0.0%
lib/policy_manager/exporter/json_view.rb	25	27	92.59%
app/helpers/policy_manager/exporter_helper.rb	14	17	82.35%
lib/policy_manager/exporter/json_link.rb	5	9	55.56%

Totals
Change from base Build 48:	10.3%
Covered Lines:	797
Relevant Lines:	874

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💛 - Coveralls