Update LSI#remove_item such that they will work with the @items hash.

https://github.com/cardmagic/classifier/pull/15
Update history to reflect merge of #2 [ci skip]
only perform first order transform if total UNIQUE words is greater than 1

https://github.com/cardmagic/classifier/pull/19
Update history to reflect merge of #3 [ci skip]
Remove mathn dependency