Updates to address memory and performance issues

On the 10% data sample, run time has been improved to between 30-60 mins, depending on the random attribute sets that are selected I suppose. Also, with the transient setting on the list of instances (in the Instances class definition), the serialized file has now been reduced from 500MB to 5MB (and now writes/reads in a few seconds).
Let me know if you have any issues with the changes.