ENH: add chainmap for easier scoping
ENH: catch key error for chainmap lookups
CLN/ENH: refactor scope to use DeepChainMap and inspect.stack
CLN/ENH: use swapkey instead of crazy hack
CLN: update expr.py for scope changes and remove unused isexpr
ENH/CLN: track scope instead of hard coding minimal stack level
BUG: allow scope usage if resolvers throw a key error but a resolver exists and not a local var
TST/CLN: more extensive scope tests
ENH: update pytables for new scoping
ERR/API: disallow local references in top-level calls to eval
CLN/API: move check for @ syntax (with engine) into _check_for_locals
BUG: globals should come before locals so that they get looked up after them
BUG: pytables name resolution must return the name if not found
TST/BUG: adhere to the API change in test_frame.py
BUG: chainmap m parameters only exists in py34
TST/CLN: add test to ensure proper date is in scope
BUG: use a regular for loop because listcomps build up stack frames
DOC: rls notes and docs re changed local variable API