Renamed bin/hooke -> bin/hk.py.

Renamed bin/hooke -> bin/hk.py.

This fixes amantedpaz' crash from
  http://code.google.com/p/hooke/issues/detail?id=40#c17
It turned out to not be related to issue8534, as I'd originally thought.

The crash looked like:
  C:\hooke>c:\python26\python bin/hooke
  ...
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
    File "c:\python26\lib\multiprocessing\forking.py", line 341, in main
      prepare(preparation_data)
    File "c:\python26\lib\multiprocessing\forking.py", line 450, in prepare
      file, path_name, etc = imp.find_module(main_name, dirs)
  ImportError: No module named hooke
  ...