doc fix
use numTrees instead of hard-coded constant
fix the inconsistent default value of numTrees in emsembleClassfier and cascadeDetector
fix threshold when learning
fix the inconsistent default value of numFeatures in emsembleClassfier and cascadeDetector
Merge pull request #46 from Dewdrops/master

Fix inconsistent value of numTrees in DetectorCascade and EnsembleClassifier