Feat/validate evidence

[satello]

• Implement Meta-Evidence features
• Split out httpRequest into it's own helper function
• Split event based Arbitrable functions into a parent class
• Implement basic ArbitrablePermissionList api

NOTE: The tests are broken

[coveralls]

Pull Request Test Coverage Report for Build 727

• 3 of 67 (4.48%) changed or added relevant lines in 9 files are covered.
• 327 unchanged lines in 11 files lost coverage.
• Overall coverage decreased (-36.5%) to 16.805%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/contracts/implementations/arbitrator/KlerosPOC.js	0	1	0.0%
src/utils/getContractAddress.js	1	2	50.0%
src/contracts/implementations/arbitrable/ArbitrableTransaction.js	0	1	0.0%
src/utils/Web3Wrapper.js	0	2	0.0%
src/contracts/implementations/arbitrable/ArbitrablePermissionList.js	0	3	0.0%
src/utils/StoreProviderWrapper.js	0	10	0.0%
src/contracts/abstractions/Arbitrable.js	0	11	0.0%
src/utils/httpRequest.js	1	15	6.67%
src/contracts/implementations/arbitrable/Arbitrable.js	1	22	4.55%

Files with Coverage Reduction	New Missed Lines	%
src/constants/error.js	1	83.67%
src/contracts/ContractImplementation.js	1	78.57%
src/contracts/abstractions/Arbitrable.js	2	0.0%
src/kleros.js	8	37.14%
src/utils/Web3Wrapper.js	9	4.0%
src/utils/StoreProviderWrapper.js	10	1.89%
src/contracts/implementations/arbitrable/ArbitrableTransaction.js	15	2.7%
src/utils/EventListener.js	41	0.0%
src/resources/Notifications.js	41	1.34%
src/resources/Disputes.js	76	5.41%

Totals
Change from base Build 719:	-36.5%
Covered Lines:	192
Relevant Lines:	936

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💛 - Coveralls