Added test case for checking missing event date in data.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@311 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Fixed citation information.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@312 edb9625f-4e0d-4859-8d74-9fd3b1da38cb