updated slides for group 2 (Random Forest)

Created by: schwarsi

new:

• explanation of parallel tree building using stratospheres deltaIterations
• example for tree-building with deltaIterations
• discussion of splitting
  • possible splits
  • metrics for 'finding' best split
  • generic example for giniIndex
• explanation of parallel splitting using stratosphere
• discussion of problems with that strategy
  • possible approaches to solve them and our choice