
1) missing condition in fp-growth
there is a missing condition in fp-growth

input database:
h,b,i,c
b,i,c,
h,i,c

epsilon=2.

fp-growth can't find the support of c,i,h because there isn't a
way to determine support of a pattern if the code has hit the single
tree condition.
the mistake is as follows:
if the minimum support in beta is sufficient to pass support
threshold, there is no problem since the minimum support cannot be
larger than "alpha"s support.
however, if there is no way to know the support of alpha alone. in
this case alpha can only be generated together with beta, which is
insufficient to pass support threshold.

solution:
determine beta's count from conut array

2) sorting of inserted transactions
 the order of all transactions must be the same, even if counts
are the same! if a and d have the same count they must always be
inserted in the same order. I implemented it in increasing index
order.
