Implemented another finding positive definite matrix algorithm
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
refactored foldRows/foldColumns a bit
refactored slice/select methods
fixed build errors
fixes #145, fixes #146
removed unused method
updated CHANGELOG
refactored min/max approaches
fixed minor issues in vector pacakge
added transormRow/transformColumn
removed safe matrices and vectors