changed citation

inst/CITATION

-citHeader("To cite the 'mixKernel' package in publications, use:")
-
-year = sub('.*(2[[:digit:]]{3})-.*', '\\1', meta$Date, perl = TRUE)
-vers = paste('R package version', meta$Version)
-
-bibentry(
-  bibtype = "Manual",
-  textVersion = paste('Mariette J., Brouard C., Flamary R., Vialaneix N. (', year, ') mixKernel: ', meta$Title, '. ', vers, '.', sep = ''),
-  author = as.person(meta$Author),
-  title = paste('mixKernel:', meta$Title),
-  year = year,
-  note = vers
-)
 
 bibentry(
   bibtype = "Article",