Initial checkin of reference implementation and the addition of folds.
added test for fold{Row,Column}(s).
Remove reference implementation.
Implemented another finding positive definite matrix algorithm
added testcase from #141
Merge pull request #134 from toddInPortland/master

Fold{Rows,Columns} implementation and Reference implementation.
fixes #143
Merge branch 'master' of github.com:vkostyukov/la4j
added credits for Leonid
added credits for Todd
added vector's test for select
Merge pull request #140 from maseev/iss12#1

New positive definite predicate implementation
a tiny refactoriing
moved contributors into the separate file
updated README