BUG: correction (t3 term) to norms.Hampel.rho and refactoring (allows b==c)
BUG: perfect prediction didn't store weights
BUG: robust.scale.Huber use mu in mad for initscale
BUG: scale.Huber previous didn't broadcast
BUG: fix norms rho, and psi
    Hampel revert typo abs, fix continuity for rho
    TukeyBiweight: add constant, so that rho(0)==0
    Hampel psi: wrong sign (this should have caused mistakes)
ENH: add rsquared, aic, bic, deviance to RLMResults
     (based on SAS definitions)
TST: update test_rlm_perfect_prediction, disable scale regression test
     (needs more work)
DOC update example script for robust scale (needs work)