Rashid/audience combinations

[rashidsp]

Summary

This adds support for audience combinations on experiments. If experiment['audienceConditions'] is present, it will be used as a condition tree where the leaf conditions are audience Ids.

• The audience evaluator uses the condition tree evaluator on both the experiment audience conditions and the individual audience conditions.
• The audience evaluator treats conditions trees and flat lists of audience ids (the old format) the same way, because a flat list of audience ids is a valid condition tree with an implicit OR condition.
• Added a new method to Experiment entity that returns audienceConditions if not None, otherwise returns audience Ids

Test plan

• test_optimizely - Added unit tests for APIs that pass/fail using various complex audiences with different match types.
• test_audience - Added new unit tests for calling condition tree and custom attribute evaluators.
• Ran complex audiences test cases in compatibility test suite.

Issues

[coveralls]

Pull Request Test Coverage Report for Build 537

• 58 of 58 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 534:	0.0%
Covered Lines:	3662
Relevant Lines:	3662

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💛 - Coveralls