#12 Deprecate combinatorial.combination_index_generator

[MATSUI Tetsushi]

combinatorial.combination_index_genarator(n, m) generates indices of m elment subsets of n element set.
It is equivalent to itertools.combinations(range(n), m)since Python 2.6.

[Tanaka Satoru]

Because of data type imcompatibilities, we stop to rewrite it.