Added to missing STL header includes
Added user-friendly laswp and NMatrix#permute_columns, as well as #permute_columns!. Includes spec.
Merge branch 'master' of github.com:SciRuby/nmatrix
History update, comments
Fixed #117
Merge branch 'master' of github.com:SciRuby/nmatrix
Merge branch 'master' of github.com:SciRuby/nmatrix