Merge v0dro's #98, hopefully fixing #70
Fixed #99 sorting problem following Yale multiplication. Switched from
selection sort to quicksort/insertion sort. Improved spec for NVector
dot NVector so that it tests not only multiplication but also quicksort
and insertion sort.
Added leakcheck script and Rake task. Changed calloc call to ALLOC_N.
Fixed memory leak: storage was being freed, but matrix struct itself was
not! Also occurring in slicing. Oops.
Fixed get_slice leak (slice was sometimes being destroyed, but
components of slice struct were not). Fixed inconsistency where list
took care of freeing insertion values but yale and dense did not.
Merge branch 'master' of https://github.com/SciRuby/nmatrix into opaque-pointers
added opaque structs in nmatrix.h