A suggestion on is_numeric function

[riversxiao]

Hi, Josh Gordon
Thanks for your great sharing, it helped me get a much better understanding of decision tree.
I have a suggestion on the function ''is_numeric''
In your example, there is no bool column in the training data, so 'is_numeric' function works fine, yet if i add a bool column in the dataset, is_numeric(True) will be true
so i suggest change the
function into the following to take bool value into account
def is_numeric(value): return type(value) in (float,int)
thanks~