Merge pull request lmfit#519 from reneeotten/PR512

updates to complement PR512

use inspect.getfullargspec for Python3

make exception explicit

remove cruft

Merge pull request lmfit#478 from reneeotten/description_pr_issues

Updates to contributing and Issue/PR templates

Merge pull request lmfit#466 from reneeotten/ampgo

Add the AMPGO algorithm

Merge pull request lmfit#462 from reneeotten/documentation_docstrings

updates to documentation and docstring

update doc for 5 digit-precision fit statistics

increase default precision for chi-square, etc from 3 to 5

correctly create non-constraint parameter values and bounds for least…

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