minor edit.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/tsdbi@519 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Additional namespace adjustments for checks in R-3.1.2. Moved zoo and
   tframePlus to Imorts from Suggests.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/tsdbi@520 edb9625f-4e0d-4859-8d74-9fd3b1da38cb