Allocation review suggestions

[szimmer]

• Update .adjust_fixed_total to set aside stratum that need to be fixed (to lbound or N.h) and THEN do allocation. Prior method could end up with a rounded allocation of 3 when the raw allocation was less than 1, makes more sense for it just to be 2.
• Update .round_fixed_total to a much simpler method based on: https://stackoverflow.com/questions/32544646/round-vector-of-numerics-to-integer-while-preserving-their-sum and remove now unnecessary .score_* functions
• Change some things from warnings to errors - when h*lbound > n.samp or sum(N.h) < n.samp