Merge pull request #2098 from embray/changelog-fixes

Fix up use of API doc references in the changelog
Conflicts:

	CHANGES.rst
Merge pull request #1461 from mdboom/wcs/docstring-generation-simplify

Simplify docstring generation in astropy.wcs
Merge pull request #2336 from embray/fix-get-graphviz-version

Fix get_graphviz_version()
Merge pull request #2324 from bsipocz/fixing_issue_2123

astropy.time.Time bugfix for issue 2123
Conflicts:

	astropy/time/core.py
Merge pull request #2337 from amras1/angle-string-padding

Fixed to_string() padding for negative angles
Use `\overset{\circ}A` for Angstrom LaTeX.
Merge pull request #2350 from mdboom/wcs/invalid-read

Fix allocation of temporary buffer in `Wcsprm.set`.
Merge pull request #2345 from embray/issue-2345

Remove platform.architecture() in FITS _array_to_file to improve speed on Mac
Merge pull request #2351 from mdboom/misc/clang-analyzer

Miscellaneous things caught by clang-analyzer.
Conflicts:

	astropy/wcs/src/wcslib_wrap.c
Merge pull request #1822 from embray/test-isolation

Fix tests that violate isolation
Conflicts:

	astropy/modeling/tests/test_models.py
Per https://github.com/astropy/astropy/issues/2290#issuecomment-40372069, removing this test as the required data file is no longer online.
Add an example.  Closes #1957 and supersedes #1959.