added several variable initializations to propitiate R CMD CHECK

for more info, see
http://stackoverflow.com/questions/9439256/how-can-i-handle-r-cmd-check-no-visible-binding-for-global-variable-notes-when
removing the RDS vignette for initial CRAN uplaod

need to figure out how to include a good sample RDS dataset before
we can include it
added CRAN-req'd details to MIT license

needed to add the file LICENSE with the year and copyright holder in it