emulator requirements

[TathagataChakraborti]

Hi @flipper83 I had some issues getting the emulator started:

• [x] File name requirements-emulator.sh ➡️ requirements-emulator.txt
• [x] Dependency issues:

ERROR: watson-developer-cloud 2.4.0 has requirement websocket-client==0.47.0, but you'll have websocket-client 0.57.0 which is incompatible.
ERROR: ibm-watson 4.0.1 has requirement websocket-client==0.48.0, but you'll have websocket-client 0.57.0 which is incompatible.

• [x] File error

Traceback (most recent call last):
  File "emulator.py", line 16, in <module>
    emulator.launch()
  File "/Users/tathagata/clai/clai/emulator/clai_emulator.py", line 44, in launch
    self.add_toolbar(self.root)
  File "/Users/tathagata/clai/clai/emulator/clai_emulator.py", line 165, in add_toolbar
    self.add_refresh_button(toolbar)
  File "/Users/tathagata/clai/clai/emulator/clai_emulator.py", line 192, in add_refresh_button
    self.refresh_image = tk.PhotoImage(file=f"{path}/refresh.png")
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/tkinter/__init__.py", line 3545, in __init__
    Image.__init__(self, 'photo', name, cnf, master, **kw)
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/tkinter/__init__.py", line 3501, in __init__
    self.tk.call(('image', 'create', imgtype, name,) + options)
_tkinter.TclError: couldn't recognize data in image file "/Users/tathagata/clai/clai/emulator/refresh.png"

• [x] **optional** Deprecation warning:

DEPRECATION WARNING: The system version of Tk is deprecated and may be removed in a future release. Please don't rely on it. Set TK_SILENCE_DEPRECATION=1 to suppress this warning.