PERF: Datetimelike lookups
cc @TomAugspurger this should address at least some of the regressions you posted about this morning.
does this link to a specific issue? > does this link to a specific issue?

Tom opened a handful of perf-regression issues yesterday.  I havent checked which of those this affects, but I think the fastpath in `__getitem__` is a big one. Thanks!