added roxygen docs
updated demos
CBG/CNBD-k now estimates k via grid search from k=1 to k=12; this requires 'litt' column to be present in CBS data set
parameter k is now part of params-vector in CBG/CNBD-k model
increased min.param.value for Maximum Likelihood search for Gamma/Gompertz
updated docs
moved demos to proper directory
Merge branch 'master' of https://github.com/mplatzer/BTYDplus

Conflicts:
	R/bg-nbd.r
	R/cbg-cnbd-k.r
	R/cbg-nbd.r
	R/gg-nbd.r
	R/nbd.r