markovchainFit should warn with list and laplace, bootstrap

[ncordon]

When we call markovchainFit with the laplace or bootstrap method, it should warn us that the method is not available for a list. For example:

c1<-c("a","b","c","c","e") 
c2<-c("a","b","d","e") 
c3<-c("a","c","b","c","d") 
c4<-c("a","b","b","d","b","c","d","e") 
c5<-c("a","c","c","d","d") 
c6<-c("a","c","d","d","b","b","e") 

mylist<-list(c1,c2,c3,c4,c5,c6) 
mylistMc<-markovchainFit(data = mylist, method = "laplace")

Related issue: #155