rm multicore reference in vignette

git-svn-id: https://hedgehog.fhcrc.org/bioconductor/trunk/madman/Rpacks/flowClust@85678 bc3139a8-67e5-0310-9ffc-ced21a209358
close #9
Merge commit 'c2d4b02464bc0785b3c1a7156ef64e333308a150' into trunk