ENH: add new computation module and toplevel eval function
ENH: rewrite assignment operator as equal comparison for PyTables
ENH: add Expr based terms for pytables
ENH: add automatic query via frame.__getitem__
ENH: add boolean operators
ENH: add chained comparisons
ENH: add subscripting to eval expressions
ENH: added interpretation of 'in' in pytables Term syntax

which is syntactically equivalent of '='
ENH: add local scoping with @lcl_variable syntax
ENH: add DataFrame.eval method
ENH: add in, not in, and string/list query support
BUG: parsing of timedelta selection syntax needed correction
CLN: correct in and not in

Also added tests for nan in and not in and disallowed ops like

    pd.eval('1 or 2')

since that should be performed in regular Python
CLN: remove __getitem__ queries
CLN/DOC: remove __getitem__ from docs
CLN: remove expr maybe_expression
Merge pull request #4164 from pydata/eval-3393

ENH: add expression evaluation functionality via eval