renamed Contingency.Rd to tables.Rd

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/vegsoup@595 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
renamed

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/vegsoup@596 edb9625f-4e0d-4859-8d74-9fd3b1da38cb