Implement get_feature_variable and create unit tests

[brandonhudavid]

Summary

• Implement get_feature_variable method in optimizely.rb to return value of variable with any type
• Changed inputs_valid? function in validator.rb to allow for nil variable type
• Create new unit tests in project_spec.rb to ensure functionality of get_feature_variable

Ruby is a dynamically-typed language, like JavaScript, so it suffices to have a single method return the value of a feature variable rather than have a separate method for each possible feature variable type.

Test plan

• Create unit tests in project_spec.rb
• Enable gherkin integration tests for Ruby in FSC suite and python-testapp

Issues

• Fulfills one of the SDK convenience APIs (design doc here)
• Passing Travis build: here

[mikeproeng37]

Mostly looks ok, just have a small comment. @msohailhussain can you also take a look when you get the chance please

[mikeproeng37]

huh? This can you explain this?

[brandonhudavid]

If variables[:variable_type] is anything other than a String or null value, it is invalid. Otherwise, it is valid, and so we remove variable_type from variables. That way, it does not go through the value.is_a?(String) && !value.empty? check on line 145.

[mikeproeng37]

Got it. Thanks

[msohailhussain]

@brandonhudavid Can you please resolve lint errors.

[coveralls]

Coverage decreased (-0.05%) to 99.467% when pulling e16983b on brandon/get_feat_var into 17c07b6 on master.

[msohailhussain]

lgtm

[mikeproeng37]

I see these two extraneous files in your commit:
experiment_to_return, and variation_to_return, can you remove em?

[mikeproeng37]

lgtm