minor improvements in SymmetricMatrixPredicate
Merge pull request #58 from ewaldgrusk/improve_symmetrix_matrix_predicate

Minor improvements in SymmetricMatrixPredicate
added credits for Ewald
fixes #59
Fix swap() method in CompressedVector class.
Also add test suite for swap();
Merge branch 'master' of https://github.com/vkostyukov/la4j.git