- redefined c(k, multiplicity) and p(k, multiplicity), so that they return 0 when multiplicity represents the empty set
- addded some tests for  c(k, multiplicity) and p(k, multiplicity)
- changed default get(index) in abstract combinatoric to support large indices.
- added methods to compute c and p in ranges of multiplicity
- added methods to compare values to c and p
- add new functions for computing combinations and permutations with 2 elements.
- add tests for combination and permutation functions.
- impremented starting iteration at a random index for permutations.
- implemented subList( from, to )
removed upcoming improvement that is implemented.
Merge pull request #10 from ctrimble/feature_perm-get-by-index

Feature perm get by index