ENH: add new computation module and toplevel eval function
BUG: prevent certain index types from joining with DatetimeIndex
ENH: rw assignment 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
BUG: provide automagic scope updating

This avoids need to pass local_dict/globals_dict explicity to
query/frame.__getitem__/eval
TST: attribute lookup on datetime.datetime (same name) was failing due to scope issues
TST: added same_name_scoping tests to io/tests/test_pytables.py
ENH: add subscripting to eval expressions
CLN/ENH: more reliable temporary variable mechanism
ENH: fail on assignment for pandas parser