NUM_THREADS should be int, not str

[Patrick Kelley]

  File ".../aardvark/local/lib/python2.7/site-packages/aardvark/manage.py", line 190, in update
    for thread_num in range(num_threads):
TypeError: <flask_script.commands.Command object at 0x7f58057aa4d0>: range() integer end argument expected, got str.

Checking out the config file generated by aardvark, it's setting the value to "1".