Merge pull request spacetelescope#197 from mcara/fix-failing-test-ast…

…ropy-dlt-fix

Fix failing test due to astropy.wcs fix for distortion look-up table bug

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release 1.7.2

tagging release 1.7.1

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tagging release 1.7.0

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tagging release 1.6.1

Tagging release 1.6.0

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