Polish testing

[loriab]

I'll fix this up when I have a clean dir and can rebase. For now, just look at the last ("adjustible") commit.

[codecov]

Codecov Report

Merging #65 into master will increase coverage by 0.43%.
The diff coverage is 93.54%.

[dgasmith]

LGTM

[loriab]

RTG. 41cdc67 is new commit. I think this is all psi needs.

[loriab]

@Lnaden here's the changelog for this PR

- (:pr:`65`) Fixed some minor printing and tolerance errors in molecule alignment.
- (:pr:`65`) ``testing.compare_molrecs`` learned parameter ``relative_geoms='align'`` that lets Molecules pass if
             geometries within a translation and rotation of each other.
- (:pr:`65`) Testing functions ``compare``, ``compare_values``, ``compare_recursive`` learned parameter
             ``return_handler`` that lets other printing, logging, and pass/fail behavior to be interjected.
- (:pr:`65`) ``testing.compare_recursive`` stopped doing ``atol=10**-atol`` for ``atol>=1``, bringing it in line with
             other compare functions.
- (:pr:`65`) ``testing.compare_recursive`` learned parameter ``forgive`` that is a list of paths that may differ without
             failing the comparison.

[dgasmith]

Levi's out for the week, could you go ahead and add to the change log?

[loriab]

981b03f pushed. included stubs. I'll take 56, 60, 62, 63

[dgasmith]

LGTM. Merge when you like.