enable rasterLayer in rangeSize function 


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/biomod@643 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
small changes

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/biomod@644 edb9625f-4e0d-4859-8d74-9fd3b1da38cb