Refactor/simplify test paths for data, training & utils

[millerjoel]

I've removed redundant path components to the tests for the data, training & utils packages. The pipeline package already had a suitable structure and tutorial package has no tests yet. All packages now follow the same structure.

The new structure, using utils for example, is:
/packages/utils/tests/*

The old structure was:
/packages/utils/tests/pyearthtools/utils/*

@tennlee Please can you check the structure I have gone with before merging? I think you had a slightly different suggestion in a comment you made in issue #36, although I'm wondering if it was a typing error. Perhaps I should have been even more ruthless with what I removed from the path?

[coveralls]

Pull Request Test Coverage Report for Build 14321333946

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 58.605%

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Totals
Change from base Build 14321327612:	0.0%
Covered Lines:	7867
Relevant Lines:	13054

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💛 - Coveralls

[tennlee]

The PR looks good. It looks like there some issues with the black reformatting. I suspect you may need to update the version of black in your environment. To keep things moving, I'll go ahead and merge the PR and then reformat those files subsequently.