Add test for eitc rate greater than 1

[hdoupe]

This test exposes the bug found in issue #596

[martinholmer]

@hdoupe, Why are you adding a TaxBrain test to detect a perfectly valid parameter value?
Look at taxcalc/current_law_policy.json to see that eitc_rt can have any non-negative value.
What am I missing? I don't see why this TaxBrain test is needed. It seems wrong, not just unneeded.

[hdoupe]

@martinholmer I added this as a regression test. I wanted to make sure that we didn't have any issues in the future with EITC_rt parameter values or values for similar parameters being rounded down to 1.

Does this clear up the confusion?

[martinholmer]

Oh, the test is to see if values of _EITC_rt greater than one are allowed.
OK, I missed that. So, adding the test seems fine.

But I don't understand the new test's docstring:

    def test_taxbrain_eitc_rt_greater_than_1(self):
        """
        Transfer over the regular tax capital gains to AMT
        """

[hdoupe]

@martinholmer Thanks for pointing that out. I copied and pasted from another function and forgot to change the docstring. The latest commit updates the docstring.

[martinholmer]

@hdoupe, #674 looks good now.

[hdoupe]

#674 test is covered in PR #706