Allow (n,1) or (1,n) arrays in C-index
Allow (n,1) or (1,n) arrays in C-index

User should not have to type A.ravel() or worse: A.values.ravel(), when
calculating the concordance index. Function now does ravel() on behalf
of the user in these two cases.

Signed-off-by: Jonas Kalderstam <35a2c6fae61f8077aab61faa4019722abf05093c@kalderstam.se>

CamDavidsonPilon/lifelines,wavelets/lifelines,nerdless/lifelines,jstoxrocky/lifelines