remove dependency on bst

demo/regression/machine.conf

@@ -7,13 +7,13 @@ objective = reg:linear
 
 # Tree Booster Parameters
 # step size shrinkage
-bst:eta = 1.0 
+eta = 1.0 
 # minimum loss reduction required to make a further partition
-bst:gamma = 1.0 
+gamma = 1.0 
 # minimum sum of instance weight(hessian) needed in a child
-bst:min_child_weight = 1 
+min_child_weight = 1 
 # maximum depth of a tree
-bst:max_depth = 3 
+max_depth = 3 
 
 # Task parameters
 # the number of round to do boosting