TST: Just import what we need.
BUG: Use matrix rank not numpy rank.
BUG: Fix import.
ENH: Use properties for dummies.
BUG: Fix logic mistake in data checkers.
TST: Add df_resid test and two test stubs.
STY: Use namespace for testing.
TST: Add sum of squares tests.
ENH: Fix degrees of freedom, bse, fvalue, and scale.
BUG: Make sure hasconst is passed up to classes.