- Update to 0.9.31:
* cleanup numpy imports to avoid deprecated functions, add financial
functions from numpy_financial module, if installed.
* prefer 'user_symbols' when initializing Interpreter, but still support
'usersyms' argument. Will deprecate and remove eventually.
* add support of optional (off-by default) "nested symbol table".
* update tests to run most tests with symbol tables of dict and nested
group type.
* general code and testing cleanup.
* add config argument to Interpreter to more fully control which nodes are supported
* add support for import and importfrom -- off by default
* add support for with blocks
* add support for f-strings
* add support of set and dict comprehension
* fix bug with 'int**int' not returning a float.