Consolidate qboost demo code

[m3ller]

Application In qboost, there are two files demo.py and demo.ipynb. I suspect the initial idea was that the user can learn through the notebook, with the option to run the code locally with the python file. However, the code in the two files have diverged a bit. Example:

# demo.py snippet
 NUM_READS = 3000
 NUM_WEAK_CLASSIFIERS = 35
 # lmd = 0.5
 TREE_DEPTH = 3

vs

# demo.ipynb snippet
NUM_READS = 1000
NUM_WEAK_CLASSIFIERS = 30
TREE_DEPTH = 2

Proposed Solution For maintainability, perhaps only have one copy of the code. Generate the other file (either .ipynb or .py) from that one copy.